When the Prophet ﷺ sat for the tashahhud, he would place his left palm on his left thigh and point with his index finger, not letting his gaze go beyond where he was pointing.
كان النبي ﷺ إذا جلس في التشهد وضع كفه اليسرى على فخذه اليسرى، وأشار بالسبابة لا يجاوز بصره إشارته.
Abu Dawud (990) and Nasai (1275) both narrated it through Yahya bin Saeed, from Ibn Ajlan, from Amir bin Abdullah bin Zubayr, from his father, who mentioned the same. Its chain is hasan because of Muhammad bin Ajlan, for he is truthful. Ibn Khuzayma graded it sahih and included it in his Sahih (718), as did Ibn Hibban (1944), through Yahya bin Saeed with the same wording. The basic hadith is found in Sahih Muslim (579), as mentioned before, through other chains from Ibn Ajlan, but without his words, "his gaze would not go beyond his gesture."