Sunan an-Nasa'i, Volume 2, Book 13, Hadith 1272 (DarusSalam) ⓘ

It was narrated from Malik bin Numair Al-Khuza'I that his father said: "I saw the Messenger of Allah putting his right hand on his right thigh when praying and pointing with his finger."

أَخْبَرَنِي 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 ‏.‏