Ibn Umar (may Allah be pleased with them both) said: On the day of the Conquest of Makkah, the Messenger of Allah (peace and blessings be upon him) entered riding the she-camel of Usamah bin Zayd (may Allah be pleased with him), until he made it kneel in the courtyard of the Ka'bah. Then he sent for the keys from Uthman bin Talhah (may Allah be pleased with him); he brought them and opened the Ka'bah. The Prophet (peace and blessings be upon him), Usamah, Bilal and Uthman bin Talhah (may Allah be pleased with them) entered, and they shut the door for a while. Then they opened the door, and I hurried forward and found Bilal (may Allah be pleased with him) at the door. I asked: Where did the Prophet (peace and blessings be upon him) pray? He said: Between the two front pillars. He said: I forgot to ask him how many rak'ahs he prayed.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 9718