The Prophet ﷺ used to point with his finger (at the end of the tashahhud) and he would not move it. Ibn Juraij said: "And 'Amr bin Dinar added: 'He (Ziyad) said: "'Amir informed me from his father that he saw the Prophet ﷺ supplicating like that. And the Prophet ﷺ would brace himself with his left hand on his left knee. (Using translation from Abū Dāʾūd 989)   

أَنَّ النَّبِيَّ ﷺ كَانَ يُشِيرُ بِأُصْبُعِهِ إِذَا دَعَا لَا يُحَرِّكُهَا قَالَ ابْنُ جُرَيْجٍ وَرَأَيْتُ عَمْرَو بْنَ دِينَارٍ قَالَ أَخْبَرَنِي عَامِرٌ عَنْ أَبِيهِ أَنَّهُ رَأَى النَّبِيَّ ﷺ يَدْعُو كَذَلِكَ يَتَحَامَلُ النَّبِيُّ ﷺ بِيَدِهِ الْيُسْرَى عَلَى رِجْلِهِ الْيُسْرَى عَلَى فَخِذِهِ وَكَذَلِكَ  

[Machine] He informed him saying, I said: "I want to observe the prayer of the Messenger of Allah ﷺ ." So he mentioned the narration and said in it, then he sat down and stretched out his left leg and placed his left hand on his left thigh and knee, and placed the edge of his right elbow on his right thigh. Then he clenched three of his fingers and made a circle, and then raised his index finger. I saw him moving it, using it as a means of supplication. It is possible that the intention of the movement is a gesture, not a repetition of the movement. This would be in accordance with the narration of Ibn Zubair. And Allah knows best.  

أَخْبَرَهُ قَالَ قُلْتُ لَأَنْظُرَنَّ إِلَى صَلَاةِ رَسُولِ اللهِ ﷺ فَذَكَرَ الْحَدِيثَ وَقَالَ فِيهِ ثُمَّ قَعَدَ فَافْتَرَشَ رِجْلَهُ الْيُسْرَى وَوَضَعَ كَفَّهُ الْيُسْرَى عَلَى فَخِذِهِ وَرُكْبَتِهِ الْيُسْرَى وَجَعَلَ حَدَّ مِرْفَقِهِ الْأَيْمَنِ عَلَى فَخِذِهِ الْيُمْنَى ثُمَّ قَبَضَ ثَلَاثَةً مِنْ أَصَابِعِهِ وَحَلَّقَ حَلْقَةً ثُمَّ رَفَعَ إِصْبَعَهُ فَرَأَيْتُهُ يُحَرِّكُهَا يَدْعُو بِهَا فَيُحْتَمَلُ أَنْ يَكُونَ الْمُرَادُ بِالتَّحْرِيكِ الْإِشَارَةَ بِهَا لَا تَكْرِيرَ تَحْرِيكِهَا فَيَكُونَ مُوَافِقًا لِرِوَايَةِ ابْنِ الزُّبَيْرِ وَاللهُ تَعَالَى أَعْلَمُ  

[Machine] Indeed, the Prophet ﷺ said that moving the finger during prayer is a cause of fear for the devil. Muhammad ibn Umar al-Waqidi did this uniquely, although it is not confirmed to be authentic. And it is narrated from Mujahid that he said moving one's finger during sitting in prayer suppresses the devil.  

أَنَّ النَّبِيَّ ﷺ قَالَ تَحْرِيكُ الْأُصْبُعِ فِي الصَّلَاةِ مَذْعَرَةٌ لِلشَّيْطَانِ تَفَرَّدَ بِهِ مُحَمَّدُ بْنُ عُمَرَ الْوَاقِدِيُّ وَلَيْسَ بِالْقَوِيِّ وَرُوِّينَا عَنْ مُجَاهِدٍ أَنَّهُ قَالَ تَحْرِيكُ الرَّجُلِ أُصْبُعَهُ فِي الْجُلُوسِ فِي الصَّلَاةِ مُقْمِعَةٌ لِلشَّيْطَانِ