Majma al-Zawaid — Hadith 808

Sayyiduna Jabir bin Abdullah (may Allah be pleased with him) narrates: Sayyiduna Umar bin al-Khattab came to the Prophet (peace and blessings be upon him) with a book (that is, a piece of writing) which he had obtained from one of the People of the Book. He began to read it before the Prophet (peace and blessings be upon him), and the Prophet (peace and blessings be upon him) became angry. He (peace and blessings be upon him) said: "O Ibn al-Khattab, is this being pondered over? By the One in whose Hand is my soul, I have brought you clear and pure teachings. Do not ask them (that is, the People of the Book) about anything, for they may tell you something true and you deny it, or they may tell you something false and you affirm it. By the One in whose Hand is my soul, even if Sayyiduna Musa (peace be upon him) were alive among you, he too would have no option but to follow me."
Ahmad, Abu Ya'la and al-Bazzar recorded it; its chain contains a narrator, Mujalid bin Sa'id, whom Ahmad, Yahya bin Sa'id and others declared da'if (weak).