Musnad Ahmad 26:887

Husayn ibn al-Hasan narrated to us, Abu Kudaynah narrated to us, from ‘Ata’ ibn al-Sa’ib, from al-Qasim ibn ‘Abd al-Rahman, from his father, from ‘Abdullah, who said: A Jew passed by the Messenger of Allah (peace and blessings of Allah be upon him) while he was speaking to his companions. The Quraysh said: "O Jew, this man claims that he is a prophet." He said: "I will surely ask him about something that no one knows except a prophet." He came and sat down, then said: "O Muhammad, from what is a human created?" He said: "O Jew, he is created from everything: from the sperm-drop of the man and from the sperm-drop of the woman. As for the sperm-drop of the man, it is a thick sperm-drop, from which are the bone and the nerve. And as for the sperm-drop of the woman, it is a thin sperm-drop, from which are the flesh and the blood." The Jew stood up and said: "That is how those before you used to say."