Sunan Ibn Majah, Hadith 1774 ⓘ
It was narrated from Ibn ‘Umar that: When the Prophet observed I’tikaf, his bedding would be spread for him, or his bed would be placed there for him, behind the Pillar or Repentance.
حَدَّثَنَا مُحَمَّدُ بْنُ يَحْيَى، حَدَّثَنَا نُعَيْمُ بْنُ حَمَّادٍ، حَدَّثَنَا ابْنُ الْمُبَارَكِ، عَنْ عِيسَى بْنِ عُمَرَ بْنِ مُوسَى، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، عَنِ النَّبِيِّ ـ صلى الله عليه وسلم ـ أَنَّهُ كَانَ إِذَا اعْتَكَفَ طُرِحَ لَهُ فِرَاشُهُ - أَوْ يُوضَعُ لَهُ سَرِيرُهُ وَرَاءَ أُصْطُوَانَةِ التَّوْبَةِ .
also referenced under: Book 7, Hadith 1846 (In-Book) & Volume 2, Book 7, Hadith 1774 (DarusSalam)