Yazid bin Abi Ubayd (may Allah have mercy on him) said: Sayyiduna Salamah bin al-Akwa' (may Allah be pleased with him) used to make a point of praying beside the pillar near which the Mushaf was kept. I said: O Abu Muslim! Why do you make a point of praying beside this particular pillar? He said: I saw the Messenger of Allah (peace and blessings be upon him): "He (peace and blessings be upon him) used to pray beside this pillar."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 10283
Nafi' narrates from Ibn Umar (may Allah be pleased with them both) that whenever the Messenger of Allah (peace and blessings be upon him) intended to perform i'tikaf, his bedding or his cot would be spread out for him beside the Pillar of Repentance, on the side facing the qiblah, and he would lean against it.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 10284
Nafi' (may Allah have mercy on him) narrates from Abdullah bin Umar (may Allah be pleased with them both) that the pillar to which Abu Lubabah (may Allah be pleased with him) tied himself is the third from the grave and the third from the courtyard.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 10285