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.
أَنَّ النَّبِيَّ ﷺ كَانَ إِذَا جَلَسَ فِي الصَّلاَةِ وَضَعَ يَدَيْهِ عَلَى رُكْبَتَيْهِ وَرَفَعَ إِصْبَعَهُ الْيُمْنَى الَّتِي تَلِي الإِبْهَامَ فَدَعَا بِهَا وَيَدَهُ الْيُسْرَى عَلَى رُكْبَتِهِ الْيُسْرَى بَاسِطُهَا عَلَيْهَا