Chapter 12: The prohibition of putting one's hand on one's waist when praying - كتاب الافتتاح
أَخْبَرَنَا حُمَيْدُ بْنُ مَسْعَدَةَ، عَنْ سُفْيَانَ بْنِ حَبِيبٍ، عَنْ سَعِيدِ بْنِ زِيَادٍ، عَنْ زِيَادِ بْنِ صُبَيْحٍ، قَالَ صَلَّيْتُ إِلَى جَنْبِ ابْنِ عُمَرَ فَوَضَعْتُ يَدِي عَلَى خَصْرِي فَقَالَ لِي هَكَذَا ضَرْبَةً بِيَدِهِ فَلَمَّا صَلَّيْتُ قُلْتُ لِرَجُلٍ مَنْ هَذَا قَالَ عَبْدُ اللَّهِ بْنُ عُمَرَ . قُلْتُ يَا أَبَا عَبْدِ الرَّحْمَنِ مَا رَابَكَ مِنِّي قَالَ إِنَّ هَذَا الصَّلْبُ وَإِنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم نَهَانَا عَنْهُ .
It was narrated that Ziyad bin Subaih said:
"I prayed beside Ibn Umar and put my hand on my waist, and he did this to me-knocked it with his hand. When I had finished praying I said to a man: 'Who is this?' He said: "Abdullah bin Umar.' I said: 'O Abu Abdur-Rahman, why are you angry with me?' He said: 'This is the posture of crucifixion, and the Mesenger of Allah (ﷺ) forbade us to do this.'"