Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) said: I asked Bilal (may Allah be pleased with him) where the Messenger of Allah (peace and blessings be upon him) prayed when he entered the House (the Ka'bah). He said: "Between these two pillars that are next to the door."
Hadith Referenceالمعجم الكبير للطبراني / باب الباء / 1040