The point at which they parted ways is their differing interpretation of the Prophet’s—peace and blessings be upon him—prohibition as stated in the ḥadith of Rāfiʿ ibn Khadīj. In that report he related:

“O Messenger of Allah, tomorrow we shall confront the enemy and we have no knives with us. May we slaughter with sharpened reeds?”

He replied, “Whatever causes the blood to flow and over which the name of Allah is pronounced—eat of it, except the tooth and the claw. Let me explain: the tooth is bone, and the claw is the knife of the Abyssinians.”

Some scholars understood from this that the underlying reason is that, by their very nature, such implements do not usually make the blood gush. Others took it to be a legal ruling for which no rationale is intended.

Those who viewed it as a non-rationalised ruling then split into three groups:

1. Some held that the prohibition renders the act invalid, so a slaughter carried out with either implement is null, even if the blood does flow.
2. Others held that the prohibition does not invalidate the act; thus, if one did use them and the blood flowed, the slaughter is valid but the person incurs sin.
3. A third group held that the prohibition signifies mere disapproval, not outright unlawfulness.

Whoever understood the ḥadith to refer to the normal inability of those tools to let the blood flow said: if the tooth or claw is fashioned in a way that the blood does flow, the slaughter is permissible. For that reason some stipulated that the tooth or claw be detached from the body, for then making the blood flow is more feasible; this is the view of Abū Ḥanīfah.

Those who held that the ruling is unreasoned and that the prohibition invalidates the act said: if either implement is used, no lawful slaughter (tadhkiyah) occurs, even if the blood gushes.

Those who held that the prohibition does not entail invalidity said: the meat is lawful if the blood is made to flow, though the user is blameworthy.

Those who regarded the prohibition as one of mere dislike found it reprehensible but did not deem it unlawful.

There is no merit in distinguishing between bone and tooth, for the Prophet—peace and blessings be upon him—explicitly forbade the tooth on the grounds that it is bone.

Nor is there any disagreement within the school that, when iron is available, using any other sharp object is disliked, based on his—peace and blessings be upon him—statement: “Indeed Allah has prescribed excellence in all things. When you kill, kill well; when you slaughter, slaughter well. Let one of you sharpen his blade and spare his animal suffering.” This was recorded by Muslim.

Chapter Four: The Conditions of Valid Slaughter
This chapter comprises three issues:

1. Pronouncing the name of Allah (tasmiya).
2. Facing the qiblah.
3. Having the proper intention.

Issue One: Pronouncing the Name
The jurists held three views regarding the legal status of pronouncing the name of Allah over the animal:

1. It is categorically obligatory. This is the position of the Ẓāhirīs, Ibn ʿUmar, al-Shaʿbī, and Ibn Sīrīn.
2. It is obligatory when one remembers, but waived in the case of forgetfulness. This is the view of Mālik, Abū Ḥanīfah, and al-Thawrī.
3. It is an emphatically recommended Sunnah. This is the position of al-Shāfiʿī and his companions, and is also narrated from Ibn ʿAbbās.