Hadith 5:147
Ibn ‘Umar said that when the Prophet observed a period of private devotion in the mosque his bedding was placed for him, or a couch was put down for him, behind the column of repentance.* *A column in the Prophet's mosque in Medina, said to have got this name because the repentance of Abu Lubaba was accepted beside it. Ibn Majah transmitted it.
عَنِ ابْنِ عُمَرَ عَنِ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ أَنَّهُ كَانَ إِذَا اعْتَكَفَ طُرِحَ لَهُ فِرَاشُهُ أَوْ يُوضَعُ لَهُ سَرِيرُهُ وَرَاءَ أسطوانه التَّوْبَة. رَوَاهُ ابْن مَاجَه
Original Reference: Mishkat al-Masabih 2107