It was narrated from Ibn ‘Umar that the Prophet ﷺ used to sit during prayer, putting his hands on his knees and raising his right finger which was next to his thumb, supplicating with it, and with his left hand (spread out) on his knee. (Using translation from Ibn Mājah 913)  

أَنَّ رَسُولَ اللهِ ﷺ كَانَ «إِذَا جَلَسَ فِي الصَّلَاةِ وَضْعَ يَدَيْهِ عَلَى رُكْبَتَيْهِ وَرَفَعَ إِصْبُعَهُ الَّتِي تَلِي الْإِبْهَامَ يَدْعُو بِهَا وَيَدُهُ الْيُسْرَى عَلَى رُكْبَتَهُ بَاسِطُهَا عَلَيْهَا»  

That the Prophet ﷺ used to point with his finger when he supplicated, but he did not move it. Ibn Jurayj said: "And 'Amr added: 'Amir bin 'Abdullah bin Az-Zubair told me that his father saw the Prophet ﷺ supplicating like that, putting his weight on his left arm, leaning on his left leg.'" (Using translation from Nasāʾī 1270)  

أَنَّ النَّبِيَّ ﷺ كَانَ «يُشِيرُ بِإِصْبُعِهِ إِذَا دَعَا وَلَا يُحَرِّكُهَا» قَالَ ابْنُ جُرَيْجٍ وَزَادَ عَمْرٌو قَالَ أَخْبَرَنِي عَامِرُ بْنُ عَبْدِ اللهِ بْنِ الزُّبَيْرِ عَنْ أَبِيهِ أَنَّهُ رَأَى النَّبِيَّ ﷺ يَدْعُو كَذَلِكَ وَيَتَحَامَلُ بِيَدِهِ الْيُسْرَى عَلَى رِجْلِهِ الْيُسْرَى