*Research paper written by Shaykh Yasir Qadhi. Originally posted on muslimmatters.org here. This article is quite detailed. For an easy summary of the conclusions go straight to the conclusion at the end.
The following is a paper presented to the AMJA Conference on The Halal and Haram in Food and Medicine (Los Angeles, California, March 2-4, 2012). Note that this paper does not represent AMJA in any way, and only represents the opinions of the author.
Terminology Equivalents Chart
Observant Muslims and Jews only eat ḥalāl and kosher products, and face many of the same problems in finding appropriate meat products in the modern, secularized world. Due to the dearth of kosher meat products available, and even higher scarcity of ḥalāl meat, many Muslims feel comfortable purchasingkosher meat, believing that all kosher meats (and by extension kosher products) are necessarily ḥalāl. Other Muslims, due to either political or theological reasons, believe that it is impermissible to purchase or consume any kosher meat products.
This paper seeks to discuss the question of the Islamic legal ruling on consuming kosher meat products. Therefore, political questions and personal values, which do not dictate the general ruling (aṣl) with respect to such products, will not be discussed.
Generally speaking (and as per Q. 4:160 and 3:50), halakhic laws are stricter than Islamic ones. This is shown not only in the foods that are permissible or impermissible, but also in the laws pertaining to slaughtering, cooking and consuming foods. Since the normative applications of Jewish law are stricter than those for Islamic law, in most cases these laws will not affect Muslims who wish to consume kosher, but would affect Jews who might be interested in ḥalāl meat. The most pertinent examples will be discussed in this paper.
Prohibitions Regarding Types of Animals and Foods
Both Jewish and Islamic laws prohibit the consumption of carrion, swine, insects, rodents and blood. Additionally, any food that is poisonous or immediately harmful to the human body would be prohibited. All solid food items prohibited by the Sharīʿa are also prohibited in Jewish law.
There are a number of significant items prohibited in the halakha but allowed by the Sharīʿa. The Qurʾān itself mentions the most common example, viz., certain types of animal fat (see Q. 6:146). Halakhic law specifies which types of fats and nerves are prohibited. The majority of madhhabs allowed the Muslim to consume these parts that are typically not considered kosher after a Jewish slaughter. The only exception to this is the Mālikī school, which deems the consumption of these parts impermissible.
Other examples of items that are prohibited for Jews but allowed for Muslims include:
– Sharks, shellfish and crustaceans (lobster, crabs, etc.) [Note: for the Ḥanafīs these animals are also not permitted].
– Some types of birds (e.g., ostrich, emu).
– Camels (because it does not have a proper ‘split hoof’).
Interestingly enough, the locust is an animal that is explicitly mentioned and allowed by both halakhic andSharʿī texts.
Also note that Jewish law forbids mixing meat and dairy products together. Different Jewish authorities have different interpretations and rules for implementation – some even require two sets of kitchen utensils and separate areas of refrigerators for these two products. There is, of course, no equivalent in Islamic law.
Jewish law also has stringent rules regarding the religious washing and usage of utensils. For example, if a ceramic or porcelain utensil is used to cook a non-kosher food, that utensil can never be purified and used for kosher cooking. However, if a metallic utensil has been used, it must be cleaned with soap and water, then left for a period of time, then immersed in boiling water under the supervision of an expert, before it may be used to cook with. Islamic law, on the other hand, would only require the regular washing of any such utensil and would permit its subsequent usage to cook or consume ḥalāl products in.
The permissibility of gelatin and rennet are ongoing discussions in both faiths. The exact same spectrum of opinions exists in both Muslim and Jewish circles. It appears that most mainstream Jewish and Muslim authorities would not permit regularly available gelatin, since it is derived from either pork or non-ritually slaughtered animals (with minority dissenting opinions on both sides). Proper kosher gelatin is therefore typically derived from kosher fish (and, in even rarer cases, from kosher slaughtered animals, or from certain cows that have died natural deaths, or from vegetable products). However, it should be noted that a product that is marked as kosher does not necessarily mean that all Jewish authorities believe it to be so. In fact, most yoghurt and candy products that are marked with circle-K are not approved by most Conservative and Orthodox Rabbis. Hence, Muslims need to know the different types of symbols used by the Jewish food industry, and their corresponding opinions, before they make a choice on whether a product that is marked as kosher is in fact ḥalāl or not.
Cheese, on the other hand, appears to be an issue where the spectrum of opinions are the same, but the majorities of each are different. Most Jewish authorities would only allow cheese if produced from kosherrennet; most Muslim authorities would allow cheese from non-ḥalāl rennet because of the issue ofistihlāk. In both groups, there are dissenting minority opinions, but the minorities are on opposite sides.
There are some halakhic restrictions on vegetables and plants (for example, the orlah, or fruit that grows during first three years after planting), and Jewish law is also stricter than Islamic law regarding insects found in fruits and vegetables, but these laws are not relevant to this discussion. Additionally, there are specific halakhic commandments for preparing Passover breads and prohibiting other foods that would also not concern Muslims.
For Muslims, the most common product that is allowed in Jewish law but prohibited in Islamic law are alcoholic beverages. Jewish law permits the consumption of ‘kosher‘ beer and wine.
Similarities in Slaughtering an Animal
Once we understand the halakhic procedure for slaughtering animals, it will be possible to arrive at an Islamic verdict regarding its status.
First, the similarities. Jewish law and Islamic law both require that:
1) The animal must be alive when it is slaughtered (hence stunning or other procedures to render the animal unconscious should be avoided).
2) The animal must be killed with a sharp knife (hence, a blow to the head would render the animal treifand ḥarām).
3) The knife must cut the neck arteries of the animal: in particular, the trachea, esophagus, cartiod arteries and jugular veins should be cut, while leaving the spinal cord intact.
4) The blood must be drained out.
5) There must be minimal harm to the animal – a painless and quick slaughter is required.
All of these are points of agreement between Jewish and Islamic law.
There are some minor differences between the requirements of the two faiths. These difference would generally be negligible and irrelevant to Muslims, but not to observant Jews.
1) Jewish law requires a specific type of person (called a shochet) to slaughter. Typically, the shochet is an observant male Jew trained in the practice of slaughter. Islamic law allows any male or female Christian, Muslim or Jew to sacrifice as long as that person follows the proper procedure of slaughtering. Therefore, it is primarily for this reason that a dhabīḥa animal can never be kosher for observant Jews because the slaughter would be performed by a Muslim.
2) The perfection of the knife blade – Jewish law requires visual and physical inspection; Islamic law only requires a sharp knife even if there are some imperfections (e.g., minor abrasions and nicks would be permissible in Islam).
3) Jewish law requires one continuous stroke for a slaughter (moving the knife back and forth would be allowed), whereas Islamic law would prefer one stroke, but the slaughter would not be invalidated if the slaughterer quickly followed a first improper stroke with another one.
4) In Jewish law, the knife must be at least two times the size of the animal’s neck, and perfectly straight, whereas there is no such requirement in Islam.
5) Jewish law completely forbids stunning, and a stunned animal would be treif; Islamic law is not unified on this point, as most authorities would consider stunning makrūh, but as long as the animal is alive and has a pulse, the slaughter would still be considered ḥalāl.
6) Depending on which Islamic madhab one followed, the number of passages in the neck of the animal cut might be less for some opinions of Islamic law (however, a perfect cut in both religions would require the esophagus, trachea, arteries and jugular).
7) While the disconnecting of the spine is prohibited in both laws, in Jewish law this would render the animal treif, whereas according to the majority opinion in Islamic law, this is makrūh but does not render the animal ḥarām (note that some authorities would view such an act as making the animal ḥarām).
8) Jewish law requires a visual inspection of the lungs and some other internal organs of the animal after slaughter. Specific defects associated with these organs makes the animal treif, whereas the total absence of any imperfection (i.e., adhesion-free lungs) renders the animal a higher level of kosher, calledglatt kosher. If such a level of perfection was not achieved, but the procedure was followed, the meat would merely be kosher. And some type of defects would in fact render the animal treif even after proper slaughter. There is no equivalent to such a post-slaughter examination in Islamic law.
9) The animal’s blood must be allowed to flow into the earth (or on the ground) in Jewish law (for example, it should not be gathered in a bowl), whereas there is no such prohibition in Islamic law. In practice, most Muslims slaughter and spill the blood on the ground as well.
10) Islamic law encourages, but does not require, that the animal faces the qiblah. Since this is not a requirement according to any madhhab, it is irrelevant to the question of whether kosher is ḥalāl.
11) While the Jewish invocation (i.e., blessing) is not a necessary requirement for the meat to be considered kosher, it is in practice never left. This issue will be discussed in a separate section.
From all of these points, it is clear that these factors will not render kosher meat ḥarām; most are in fact rulings that make the halakhic laws stricter than their Sharʿī equivalents, and even the Islamic ones on this list are recommendations and not requirements. Hence, from the perspective of the Sharīʿa, these factors are not relevant.
Of course, because of some or most of these factors (especially the first one), ḥalāl meat cannot be considered kosher by Jewish authorities.
Major Difference – the Tasmiya Issue
There is one major differences between the two laws that cannot be overlooked and could potentially result in a verdict of taḥrīm, and that is the issue of the tasmiya.
The Islamic opinions on mentioning Allāh’s name at the time of sacrifice are well-known. It is clear that the majority of scholars (and the explicit texts of the Qurʿān and Sunnah) require the utterance of tasmiyabefore an animal is slaughtered. It is with this opinion in mind that we proceed. (It goes without saying that, for the minority who do not require tasmiya, obviously if they do not require a Muslim to mention the name of Allāh then a priori they would not require a non-Muslim to do so).
Halakhic law states that the shochet should verbally bless the act of slaughter with a specific blessing.While this blessing is not considered an essential requirement, in practice it is always done, and it is realistically inconceivable that a shochet intentionally abandons this blessing.
The formulation of this blessing translates as:
“Blessed are you , Adonai [G-d], our G-d, Lord of the World, Who Sanctified us through His Commandments and instructed us concerning proper animal slaughter”
The wording clearly praises God, and therefore would be acceptable to the vast majority of madhhabs,since it is not a necessary requirement that the blessing be said in Arabic. However, the issue comes with respect to a unique blessing for each animal.
Since the Jewish faith insists that the name of the Lord only be invoked with good cause, the shochet does not repeat this blessing for each and every animal. Instead, the shochet considers one blessing to suffice for a series of animals with the condition that each animal is slaughtered without any significant pause or break from the previous one. 
Therefore, in theory, a shochet could sacrifice a few cows, and maybe even up to a hundred chicken, with one blessing.
All of this, of course, has relevance to the Sharʿī ruling on an animal.
For the minority that does not require tasmiya (in particular, the Shāfʿī school), this issue would not be relevant, and therefore kosher would be ḥalāl.
For those who subscribe to the position that allows one tasmiya for multiple slaughters, kosher meat would also be ḥalāl.
For those who require a specific tasmiya for each individual animal (in particular, the Ḥanafī school),kosher meat would not be ḥalāl unless it was known for sure that a blessing was given for that animal.
As a side point, there are reference to some Christian groups who required a slaughterer to sacrifice in the name of God.
In light of all that has preceded, and in this author’s opinion:
– While the Qurʿān explicitly allows us to offer (and therefore sell) ḥalāl meat to Jews, most observant Jews would not consider ḥalāl to be kosher because the animal would be slaughtered by a non-Jew (and there would be other factors as well).
– All kosher foods are permissible as long as 1) no significant amount of alcohol is present, and 2) any gelatin is from kosher slaughtered cattle or non-animal sources. If alcohol is used either for taste or in intoxicating amounts, the food prepared would be ḥarām; and any gelatin derived from animals not slaughtered with tasmiya is also ḥarām.
– Kosher meat being ḥalāl would depend on which madhhab one follows for the tasmiya: if one follows the opinion that one tasmiya suffices for multiple animals, kosher slaughtered animals would be ḥalāl. However, if one requires one tasmiya per animal, then in general such animals would be ḥarām unless one can verify that the blessing was said for that particular animal.
In this author’s opinion, since the halakhic blessing is done over a specific group of animals and the slaughter is continuous, this blessing can suffice to fulfill the requirements of the tasmiya for that group of animals, and Allāh knows best.
Lastly, it is important that stronger ties be developed between observant Muslims and Jews so that we benefit from each other’s experiences, unite against Islamophobic and anti-Semitic efforts to ban ritual animal slaughter, and perhaps also manage to influence some kosher plants to say a tasmiya for every animal.
 This is based on Leviticus 7:3. Generally, Jewish law does not allow fat surrounding the kidneys, the abdominal fats, the fats surrounding the stomach and intestines, and the tail fat. The nerve that is forbidden is one that is in the hind-quarters. Since it is labor-intensive to remove this nerve, generally the hind-quarters of an animal are sold to non-Jews.
 Many Qurʿānic exegetes consider this to be an example of Q. 3:93; others also add the ruling of animal fats, but this latter opinion clearly contradicts Q. 6:146.
 This discussion is necessarily simplistic and brief.
 These are so-called ‘Indian cows’; since Hindus are not allowed to kill cows, any cow that dies is left untouched. Jewish law allows the bones of such an animal, if left untouched for a long period of time, to be used for the manufacture of gelatin.
 I have written a paper about this, published online. See: http://muslimmatters.org/2007/07/09/of-mice-and-men-the-cheese-factor/.
 Since this law is irrelevant to the halakha, some modern Jewish authorities have allowed taking this condition into account when performing kosher slaughters.
 Of course, we are not talking about the issue of adding alcohol to the meat while it is being cooked. Jewish law permits the consumption of certain types of alcohol and the mixing of wine with meat products. Any such production of meat would obviously be ḥarām for Muslims.
 It is relevant to point out that Ibn Ḥanbal’s position regarding the tasmiya for Ahl Kitāb sacrifices is explicit – and as far as I know, everything narrated to the contrary is mujmal. Ḥanbal reports that Abū Abdillāh said, “There is no problem with the sacrifice of the Kitābī as long as he sacrifices for Allāh and in the name of Allāh (idhā ahallū lillāhi wa sammū ʿalayhī).” [Aḥkām Ahl al-Dhimmah, 1/189]. This was also the explicit position of Ibn Taymiyya and Ibn al-Qayyim. It should also be noted that most authorities who allowed the sacrifice of the Kitābī without mentioned Allāh’s name also allowed it if they mentioned other than Allāh’s name [ibid., 1/191-3].
Also, the reader is encouraged to see Ibn Taymiyya’s risāla on this issue, in Jāmiʾ al-Masāʾil of Dr. Bakr Abu Zayd (Riyad: Dār al-ʿĀlim, 1429), vol. 6, p. 377-89. In it, he states that the obligation of saying thetasmiya before hunting or slaughtering an animal is even more clear than the obligation to recite Fātiḥa in the prayer.
It is the intention of the author to write a brief treatise on this issue as well, insha Allāh.
 It is important to note that the blessing is for the act of sacrifice, and not for an animal or for the instrument.
 Therefore, from an Islamic standpoint, the shochet who does not mention the blessings will be fī ḥukm al-nāsī (i.e., the one who accidentally forgets), and the majority of scholars would deem such a slaughter as permissible, in contrast to the one who intentionally does not mention Allāh’s name.
 Most modern Rabbis allow the shochet to utter the phrase ‘bismillāh Allahu akbar‘ in Arabic before each slaughter, since that does not interfere with the rules of halakha. This practice should be encouraged and Muslims should inform local Jewish slaughterhouses that they would become potential customers if the shochet could do this.
 In the Syriac-language Nomocanon of Barhebraeus (d. 1286), a Christian butcher is instructed to recite the phrase ba-shma d’elaha haya, “In the name of the living God.” Gregorius Barhebraeus,Nomocanon, ed. Paul Bedjan (Paris: Harrassowitz, 1898); taken from Freidenreich (cit.)