صَحِيحُ مُسْلِمٍ
Sahih Muslim 580 a
The Book of Mosques and Places of Prayer
The description of the sitting during the prayer, and how the hands are to be placed on the thighs
وَحَدَّثَنِي مُحَمَّدُ بْنُ رَافِعٍ، وَعَبْدُ بْنُ حُمَيْدٍ، قَالَ عَبْدٌ أَخْبَرَنَا وَقَالَ ابْنُ رَافِعٍ، حَدَّثَنَا عَبْدُ الرَّزَّاقِ، أَخْبَرَنَا مَعْمَرٌ، عَنْ عُبَيْدِ اللَّهِ بْنِ عُمَرَ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، أَنَّ النَّبِيَّ صلى الله عليه وسلم كَانَ إِذَا جَلَسَ فِي الصَّلاَةِ وَضَعَ يَدَيْهِ عَلَى رُكْبَتَيْهِ وَرَفَعَ إِصْبَعَهُ الْيُمْنَى الَّتِي تَلِي الإِبْهَامَ فَدَعَا بِهَا وَيَدَهُ الْيُسْرَى عَلَى رُكْبَتِهِ الْيُسْرَى بَاسِطُهَا عَلَيْهَا .
Ibn 'Umar reported that when the Messenger of Allah (ﷺ) sat for tashahhud he placed his left hand on his left knee. and his right hand on his right knee. and he raised his right finger, which is next to the thumb, making supplication in this way, and he stretched his left hand on his left knee.
Sahih Muslim, 580 aSahihصحيح