Imam al-Shafi'i (may Allah have mercy on him) said: "Allah, the Blessed and Exalted, says: 'All food was lawful to the Children of Israel except what Israel (that is, Ya'qub (peace be upon him)) had made unlawful for himself.' [Surah Al Imran: 93] (the verse)."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الضحايا / Q19702
It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that Israel (that is, Ya'qub (peace be upon him)) was afflicted with sciatica, and he would spend the night crying out (in pain). He said: So he vowed that if Allah cured him, he would not eat meat that contains veins. He said: Then the Jews made it unlawful, so this verse was revealed: "All food was lawful to the Children of Israel except what Israel made unlawful for himself before the Torah was revealed. Say: Then bring the Torah and recite it, if you are truthful." [Surah Al Imran: 93] That is, this was before the Torah. Sufyan said: Zuqa' means crying out. Imam al-Shafi'i (may Allah have mercy on him) said concerning "Because of the wrongdoing of the Jews, We made unlawful for them good things which had been lawful for them." [Surah al-Nisa: 160] that, and Allah knows best, they are the good things that had been made lawful for them.
"And to the Jews We made unlawful every animal with claws, and of cattle and sheep We made unlawful for them their fat, except what clings to their backs, or to the entrails, or what is mixed with bone." [Surah al-An'am: 146]
Imam al-Shafi'i (may Allah have mercy on him) said: "Al-hawaya" (the entrails) means that which encloses food and drink in the belly.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الضحايا / 19702
Ibn Abbas (may Allah be pleased with them both), concerning "every animal with claws" [Surah al-An'am: 146], said: It means the camel and the ostrich. And concerning His words "except what their backs carry" [Surah al-An'am: 146], he said: It means the fat that clings to the back; and "or the entrails" [Surah al-An'am: 146] means the intestines (where the dung collects).
Ibn Abi Najih narrated the same meaning from Mujahid (may Allah have mercy on him), as his own words, in explaining "every animal with claws" and "the entrails".
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الضحايا / 19703
Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) said: It is the firm covenant that Allah Almighty had taken from them regarding what He had made unlawful for them, that He would remove those things from them.
Imam al-Shafi'i (may Allah have mercy on him) said: Since Allah, the Mighty and Majestic, sent Muhammad (peace and blessings be upon him), there has remained no rational creature, of jinn or of mankind, whom the call of the Prophet (peace and blessings be upon him) has reached except that the proof of Allah has been established against him to follow his (peace and blessings be upon him) religion. And it became binding on every person to hold unlawful what Allah Almighty made unlawful on the tongue of His Prophet (peace and blessings be upon him), and to hold lawful what the Prophet (peace and blessings be upon him) made lawful.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الضحايا / 19704
Jabir (may Allah be pleased with him) said: Nu'man bin Qawqal (may Allah be pleased with him) came to the Prophet (peace and blessings be upon him) and said: O Messenger of Allah (peace and blessings be upon him)! What is your view: if I pray the obligatory prayers, regard the unlawful as unlawful and the lawful as lawful, will I enter Paradise? He (peace and blessings be upon him) said: "Yes."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الضحايا / 19705
It is narrated from Sayyiduna Ma'qil bin Yasar (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Act upon the Qur'an: regard its lawful as lawful and its unlawful as unlawful, follow it, and do not deny anything of it. Whatever of it becomes doubtful to you, refer it back to Allah and to the people of knowledge after me, who will inform you. Believe in the Torah, the Injil, the Zabur and what the prophets were given from their Lord. The Qur'an and what is in it is sufficient for you, for it is an intercessor whose intercession will be accepted, and its lawful things have been confirmed. Beware! Every verse will be a light on the Day of Resurrection. I have been given Surah al-Baqarah from the first remembrance; I have been given Ta Ha and the surahs that begin with Ta Sin and Ha Mim from the Tablets of Musa (peace be upon him); and I have been given Surah al-Fatihah from beneath the Throne."
Ubaydullah bin Abi Humayd has been criticised (by the scholars of hadith).
Imam al-Shafi'i (may Allah have mercy on him) said: Allah made lawful the food of the People of the Book, and according to the people of tafsir this means their slaughtered animals; He did not except anything from them. So it cannot be that the slaughtered animal of a person of the Book is lawful while something in that slaughtered animal is unlawful for every Muslim, from what had been made unlawful for the People of the Book before the Prophet (peace and blessings be upon him).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الضحايا / 19706
Abdullah bin Mughaffal (may Allah be pleased with him) said: On the day of Khaybar I got a bag of fat, and I kept it aside. I said: I will not give anyone anything from it. I turned around and saw that the Prophet (peace and blessings be upon him) was smiling.
Note: If the fat from the slaughtered animal of the People of the Book is permissible, then the slaughtered animal is also permissible.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الضحايا / 19707
Abdullah bin Mughaffal (may Allah be pleased with him) said: On the day of Khaybar I got a bag of fat, and I held on to it. I said: "This is mine; I will not give anyone anything." I turned around and saw that the Prophet (peace and blessings be upon him) was smiling, and I felt shy before him (peace and blessings be upon him).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الضحايا / 19708