Sahih Bukhari
Pilgrimmage (Hajj)
Volume: 002 / Book Number: 026 / Hadith Number: 668
Narrated Salim that his father said,
"Allah's Apostle, Usama bin Zaid, Bilal, and 'Uthman bin abu Talha entered the Ka'ba and then closed its door. When they opened the door I was the first person to enter (the Ka'ba). I met Bilal and asked him, "Did Allah's Apostle offer a prayer inside (the Ka'ba)?" Bilal replied in the affirmative and said, "(The Prophet offered the prayer) in between the two right pillars."