Narrated Abu Huraira:
When Khaibar was conquered, a roasted poisoned sheep was presented to the Prophets as a gift (by the Jews). The Prophet ordered, "Let all the Jews who have been here, be assembled before me." The Jews were collected and the Prophet said (to them), "I am going to ask you a question. Will you tell the truth?'' They said, "Yes.' The Prophet asked, "Who is your father?" They replied, "So-and-so." He said, "You have told a ie; your father is so-and-so." They said, "You are right." He siad, "Will you now tell me the truth, if I ask you about something?" They replied, "Yes, O AbuAl-Qasim; and if we should tell a lie, you can realize our lie as you have done regarding our father." On that he asked, "Who are the people of the (Hell) Fire?" They said, "We shall remain in the (Hell) Fire for a short period, and after that you will replace us." The Prophet said, "You may be cursed and humiliated in it! By Allah, we shall never replace you in it.'' Then he asked, "Will you now tell me the truth if I ask you a question?" They said, "Yes, O Ab Li-AI-Qasim." He asked, "Have you poisoned this sheep?" They said, "Yes." He asked, "What made you do so?" They said, "We wanted to know if you were a liar in which case we would get rid of you, and if you are a prophet then the poison would not harm you."