It is narrated from Sayyiduna Anas bin Malik (may Allah be pleased with him) that he was asked: "When the Messenger of Allah (peace and blessings be upon him) entered the House (the Ka'bah), where did he (peace and blessings be upon him) pray?" He said: "Between the two pillars."
Hadith Referenceالمعجم الأوسط / باب الجيم / 3373
Hadith Takhrij«أخرجه الطبراني فى «الصغير» برقم: 326»