Musannaf Ibn Abi Shayba 33:211

Yazid ibn Harun narrated to us, he said: Hammad ibn Salamah informed us, from Thabit, from Anas, who said: Abu Bakr used to deliver sermons to us, and he would mention the beginning of the creation of man. He would say: "He was created from the passage of urine, from filth." He would continue mentioning [such things] until one of us would feel disgusted with himself.