Musnad Ahmad 119:4

Ahmad ibn al-Hajjaj narrated to us, Jarir informed us, from Yazid ibn Abi Ziyad, from Mujahid, from Abd al-Rahman ibn Safwan, who said: When the Messenger of Allah, peace and blessings of Allah be upon him, conquered Makkah, I said: "I will put on my clothes," and my house was on the road, "so that I may see what the Messenger of Allah, peace and blessings of Allah be upon him, does." So I set out, and I encountered the Messenger of Allah, peace and blessings of Allah be upon him, having come out of the Kaaba, and his companions had touched the House from the door to the al-Hatim, and they had placed their cheeks upon the House, and the Messenger of Allah, peace and blessings of Allah be upon him, was in their midst. I said to Umar: "And what did the Messenger of Allah, peace and blessings of Allah be upon him, do when he entered the Kaaba?" He said: "He prayed two rak'ahs."