Sunan an-Nasai 16009
In-book no 1273أَخْبَرَنِي مُحَمَّدُ بْنُ عَبْدِ اللَّهِ بْنِ عَمَّارٍ الْمَوْصِلِيُّ، عَنِ الْمُعَافَى، عَنْ عِصَامِ بْنِ قُدَامَةَ، عَنْ مَالِكٍ، - وَهُوَ ابْنُ نُمَيْرٍ الْخُزَاعِيِّ - عَنْ أَبِيهِ، قَالَ رَأَيْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم وَاضِعًا يَدَهُ الْيُمْنَى عَلَى فَخِذِهِ الْيُمْنَى فِي الصَّلاَةِ وَيُشِيرُ بِأُصْبُعِهِ .
It was narrated from Malik bin Numair Al-Khuza'I that his father said: "I saw the Messenger of Allah (ﷺ) putting his right hand on his right thigh when praying and pointing with his finger."