Thauban, the freed slave of the Messenger of Allah (ﷺ), said:
While I was standing beside the Messenger of Allah (ﷺ) one of the rabbis of the Jews came and said: Peace be upon you, O Muhammad. I pushed him backwith a push that he was going to fall. Upon this he said: Why do you push me? I said: Why don’t you say: O Messenger of Allah? The Jew said: We call him by the name by which he was named by his family. The Messenger of Allah (ﷺ) said: My name is Muhammad with which I was named by my family. The Jew said: I have come to ask you (something). The Messenger of Allah (ﷺ) said: Should that thing be of any benefit to you, if I tell you that? He (the Jew) said: I will lend my ears to it. The Messenger of Allah (ﷺ) drew a line with the help of the stick that he had with him and then said: Ask (whatever you like). Thereupon the Jew said: Where would the human beings be on the Day when the earth would change into another earth and the heavens too (would change into other heavens)? The Messenger of Allah (ﷺ) said: They would be in darkness beside the Bridge. He (the Jew) again said: Who amongst people would be the first to cross (this bridge).? He said: They would be the poor amongst the refugees. The Jew said: What would constitute their breakfast when they would enter Paradise? He (the Holy Prophet) replied: A caul of the fish-liver. He (the Jew) said. What would be their food after this? He (the Holy Prophet) said: A bullock which was fed in the different quarters of Paradise would be slaughtered for them. He (the Jew) said: What would be their drink? He (the Holy Prophet) said: They would be given drink from the fountain which is named “Salsabil”. He (the Jew) said: I have come to ask you about a thing which no one amongst the people on the earth knows except an apostle or one or two men besides him. He (the Holy Prophet) said: Would it benefit you if I tell you that? He (the Jew) said: I would lend ears to that. He then said: I have come to ask you about the child. He (the Holy Prophet) said: The reproductive substance of man is white and that of woman (i.e. ovum central portion) yellow, and when they have sexual intercourse and the male’s substance (chromosomes and genes) prevails upon the female’s substance (chromosomes and genes), it is the male child that is created by Allah’s Decree, and when the substance of the female prevails upon the substance contributed by the male, a female child is formed by the Decree of Allah. The Jew said: What you have said is true; verily you are an Apostle. He then returned and went away. The Messenger of Allah (ﷺ) said: He asked me about such and such things of which I have had no knowledge till Allah gave me that.
Sahih Muslim 315 a
In-book : Book 3, Hadith 38