When the Messenger of Allah ﷺ sat for the tashahhud, he would place his left palm on his left thigh and point with his index finger, his gaze not extending beyond the point of his finger.
أخبرنا يعقوب بن إبراهيم قال حدثنا يحيى عن ابن عجلان
أن رسول الله ﷺ كان إذا قعد في التشهد وضع كفه اليسرى على فخذه اليسرى وأشار بالسبابة لا يجاوز بصره إشارته
Muslim narrated it in the Book of Mosques, chapter on the manner of sitting in prayer and how to place the hands on the thighs, hadith no. 113/579, from the hadith of Ibn Ajlan, through this chain. He made explicit the hearing [from his teacher] in Ahmad's version, 3/4, and it is also found in Kubra, hadith no. 1198.