Sayyiduna Ibn Umar (may Allah be pleased with them both) said: In the year of the Conquest (of Makkah), the Prophet (peace and blessings be upon him) came riding on the she-camel named al-Qaswa' with Sayyiduna Usamah (may Allah be pleased with him) seated behind him. Sayyiduna Bilal and Uthman bin Talhah (may Allah be pleased with them both) were also with him (peace and blessings be upon him), until the mount was made to kneel by the House of Allah. Then he said to Sayyiduna Uthman (may Allah be pleased with him): "Bring the key." He brought the key and opened the door for him (peace and blessings be upon him). Then he (peace and blessings be upon him), Sayyiduna Usamah, Bilal and Uthman (may Allah be pleased with them) entered. Then they closed the door and spent a long part of the day there. Then he (peace and blessings be upon him) came out, and the people hurried to enter; I got ahead of all of them, and there I found Sayyiduna Bilal (may Allah be pleased with him) standing behind the door. I asked him: Where did the Messenger of Allah (peace and blessings be upon him) pray? He said: Between the two front pillars; and in those days the House of Allah had six pillars, in two rows. He (peace and blessings be upon him) prayed between the pillars of the front row, and the door of the House of Allah was behind his (peace and blessings be upon him) back. He (peace and blessings be upon him) turned his blessed face toward the place that comes directly in front of a person when he enters the House of Allah, and prayed between himself and the wall.
Sayyiduna Ibn Umar (may Allah be pleased with them both) said: I forgot to ask Sayyiduna Bilal (may Allah be pleased with him) how much the Messenger of Allah (peace and blessings be upon him) prayed, and at the place where he (peace and blessings be upon him) had prayed there was red marble.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3783