"When the Prophet would sit during the Salat, he would place his right hand on his knee, and raise his finger, the one that is next to the [right] thumb, supplicating with it, and his left hand was spread flat on his left knee."  

أَنَّ النَّبِيَّ ﷺ كَانَ إِذَا جَلَسَ فِي الصَّلاَةِ وَضَعَ يَدَهُ الْيُمْنَى عَلَى رُكْبَتِهِ وَرَفَعَ إِصْبَعَهُ الَّتِي تَلِي الإِبْهَامَ الْيُمْنَى يَدْعُو بِهَا وَيَدُهُ الْيُسْرَى عَلَى رُكْبَتِهِ بَاسِطَهَا عَلَيْهِ قَالَ وَفِي الْبَابِ عَنْ عَبْدِ اللَّهِ بْنِ الزُّبَيْرِ وَنُمَيْرٍ الْخُزَاعِيِّ وَأَبِي هُرَيْرَةَ وَأَبِي حُمَيْدٍ وَوَائِلِ بْنِ حُجْرٍ