Musannaf Ibn Abi Shayba 3:6425

Yazid ibn Harun narrated to us, he said: Ibn Abi Dhi'b narrated to us, from Muslim ibn Jundub, from al-Harith ibn al-Barsa', who said: Khubayb was brought and sold in Mecca. They took him out of the Sacred Precinct (al-Haram) to kill him. He said: "Let me pray two rak'ahs." So they left him, and he prayed two rak'ahs. Then he said: "Were it not that you would think I am showing impatience, I would have added more."