Musannaf Ibn Abi Shayba 1:965

965. Ubayd Allah ibn Musa narrated to us, from Shayban, from Yahya, from Abu Salamah, that Ata ibn Yasar informed him that Zayd ibn Khalid al-Juhani informed him that he asked Uthman ibn Affan. He said: I said, "What is your opinion if a man has intercourse with a woman but does not ejaculate?" Uthman said: "He performs ablution like his ablution for prayer and washes his private part." And Uthman said: "I heard that from the Messenger of Allah (may Allah bless him and grant him peace)." He said: And I asked Ali, al-Zubayr, Talhah, and Ubayy ibn Ka'b about that, and they commanded him to do that.