Musannaf Ibn Abi Shayba 1:940

Ibn Idris narrated to us, from al-Shaybani, from Bukayr ibn al-Akhnas, from Sa’id ibn al-Musayyib, who said: Umar said: "I will not be brought a man who did it—meaning he had intercourse—and then did not ejaculate and did not perform ghusl, except that I will punish him severely."