Musnad Ahmad 32:1924

'Affan narrated to us, Hammad narrated to us, Thabit and Humayd informed us, from Anas ibn Malik, who said: When the Messenger of Allah (peace and blessings of Allah be upon him) arrived in Medina, 'Abdullah ibn Salam was informed of his arrival while he was among his palm trees. He came to him and said: "I am going to ask you about things that no one knows except a prophet. If you inform me of them, I will believe in you; and if you do not know them, I will know that you are not a prophet." He said: So he asked him about the resemblance (of a child to its parents), about the first thing the people of Paradise will eat, and about the first thing that will gather the people. The Messenger of Allah (peace and blessings of Allah be upon him) said: "Gabriel has just informed me of them." He said: "That is the enemy of the Jews." He said: "As for the resemblance: if the man's fluid precedes the woman's fluid, the resemblance goes to him; and if the woman's fluid precedes the man's fluid, the resemblance goes to her. As for the first thing the people of Paradise will eat, it is the extra lobe of a whale's liver. As for the first thing that will gather the people, it is a fire that will emerge from the direction of the east and gather them toward the west." So he believed and said: "I bear witness that you are the Messenger of Allah." Ibn Salam said: "O Messenger of Allah, the Jews are a people of slander, and if they hear of my Islam, they will slander me. So hide me with you, and send for them and ask them about me." The Messenger of Allah (peace and blessings of Allah be upon him) hid him, and sent for them. They came, and he said: "What kind of man is 'Abdullah ibn Salam among you?" They said: "He is the best of us and the son of the best of us, our master and the son of our master, our scholar and the son of our scholar." He said: "Do you see, if he were to become Muslim, would you become Muslim?" They said: "May Allah protect him from that." He said: "O 'Abdullah ibn Salam, come out to them and inform them." So he came out and said: "I bear witness that there is no god but Allah, and I bear witness that Muhammad is the Messenger of Allah." They said: "He is the worst of us and the son of the worst of us, the most ignorant of us and the son of the most ignorant of us." Ibn Salam said: "I have already informed you, O Messenger of Allah, that the Jews are a people of slander."