مِشْكَاةُ الْمَصَابِيحِ
Mishkat al-Masabih 1003
Prayer
What may not be done during Prayer and what is permitted - Section 2
وَعَنِ ابْنِ عُمَرَ رَضِيَ اللَّهُ عَنْهُمَا قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «الِاخْتِصَارُ فِي الصَّلَاةِ رَاحَةُ أَهْلِ النَّارِ» . رَوَاهُ فِي شرح السّنة
Ibn ‘Umar reported God’s Messenger as saying, “Resting the hands on the waist in prayer is the comfort of those who go to hell.” [Baghawi] transmitted it in Sharh as-sunna.
Mishkat al-Masabih, 1003مُنكر (الألباني)