It is narrated from Sayyiduna Jabir (may Allah be pleased with him) that once Sayyiduna Umar came to the service of the Prophet (peace and blessings be upon him) with a book that he had obtained from a person of the People of the Book, and he began to read it before the Prophet (peace and blessings be upon him). At this, the Prophet (peace and blessings be upon him) became angry and said, "O Ibn Khattab, are you inclined towards this? By Him in Whose hand is my soul, I have brought to you a Shariah that is clear and pure. Do not ask the People of the Book about anything, for it may be that they tell you something true and you deny it, or they tell you something false and you affirm it. By Him in Whose hand is my soul, if Musa (Moses) were alive, he would have no choice but to follow me."