It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that when the Prophet (peace and blessings be upon him) observed i'tikaf, his bedding and his couch (peace and blessings be upon him) would be laid out for him by the Pillar of Repentance, on the side facing the qiblah, and then he (peace and blessings be upon him) would lean against it.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 13367