´'Amr bin 'Abdullah bin Az-Zubair narrated that:` His father said: "When the Messenger of Allah (ﷺ) sat in the second or fourth rak'ah, he would place his hands on his knees and point with his finger."
Explanation & Benefits
Hafiz Muhammad Ameen
1162. Commentary: The manner, Sunnah status, and position of the gesture in Tashahhud have already been discussed in detail under Hadith number 890 and its benefits. In summary, the index finger of the right hand should be kept raised in a gesture from the beginning of the sitting (qa'dah) until the end. Some people say that the finger should be raised or moved at "ashhadu an la ilaha" and then lowered at "illa Allah," but there is no evidence for this. The ahadith indicate that the finger should remain raised until the very end, i.e., until the salam is given, and at times, in some prayers, the finger remains in motion throughout the entire Tashahhud until the salam. Both methods are correct and Sunnah. And Allah knows best.
Source: Sunan Nasa'i: Translation and Benefits by Shaykh Hafiz Muhammad Amin Hafizullah, Page: 1162