‘Abd Allah b. al-Zubair said: When the Messenger of Allah(ﷺ) sat during the prayer( at the tashahhud), he placed his left foot under his right thigh and shin and spread his right foot and placed his left hand on his left knee and placed his right hand on his right thigh, and he pointed with his forefinger.
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا مُحَمَّدُ بْنُ عَبْدِ الرَّحِيمِ الْبَزَّازُ، حَدَّثَنَا عَفَّانُ، حَدَّثَنَا عَبْدُ الْوَاحِدِ بْنُ زِيَادٍ، حَدَّثَنَا عُثْمَانُ بْنُ حَكِيمٍ، حَدَّثَنَا عَامِرُ بْنُ عَبْدِ اللَّهِ بْنِ الزُّبَيْرِ، عَنْ أَبِيهِ، قَالَ كَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم إِذَا قَعَدَ فِي الصَّلاَةِ جَعَلَ قَدَمَهُ الْيُسْرَى تَحْتَ فَخِذِهِ الْيُمْنَى وَسَاقِهِ وَفَرَشَ قَدَمَهُ الْيُمْنَى وَوَضَعَ يَدَهُ الْيُسْرَى عَلَى رُكْبَتِهِ الْيُسْرَى وَوَضَعَ يَدَهُ الْيُمْنَى عَلَى فَخِذِهِ الْيُمْنَى وَأَشَارَ بِأُصْبُعِهِ . وَأَرَانَا عَبْدُ الْوَاحِدِ وَأَشَارَ بِالسَّبَّابَةِ .
sunnah.com