Sahih Muslim
The Book of Oaths (Kitab Al-Aiman)
Book Number: 015 / Hadith Number: 4076
Nafi' reported: A mention of Allah's Messenger (may peace be upon him) observing 'Umra from ja'rina was made before Ibn 'Umar. He said: He did not enter into the state of Ihram from that (place), and Umar had taken a vow of observing I'tikaf for a night during the days of Ignorance. The rest of the hadith is the same.