Sahih
Muslim
صحيح مسلم
The Book of Mosques and Places of Prayer
كتاب الْمَسَاجِدِ وَمَوَاضِعِ الصَّلاَةِ
Chapter 21: The description of the sitting during the prayer, and how the hands are to be placed on the thighs
باب صِفَةِ الْجُلُوسِ فِي الصَّلاَةِ وَكَيْفِيَّةِ وَضْعِ الْيَدَيْنِ عَلَى الْفَخِذَيْنِ
Sahih Muslim 580 a
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.
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 .