Tirmidhi

Explanation:
1:
As the author himself has explained, this is regarding making a gesture with the index finger during the tashahhud (the first and second sitting in prayer).
From the very beginning of the tashahhud, one should form a circle with the thumb and middle finger, and continuously bear witness to the oneness of Allah by repeatedly raising the index finger,
not only at (ashhadu alla ilaha illallah) as has become customary in the Indian subcontinent.
It is explicitly stated in the hadith that the Messenger of Allah (sallallahu alayhi wa sallam) would form a circle with his fingers and gesture with the index finger,
or keep moving it.
There is no restriction regarding the place (in the tashahhud) for this action.

1273. Commentary: The gesture with two fingers will either be with two fingers of the right hand itself, or it is also possible that it is with the index fingers of both hands. Since this gesture is a practical expression of tawhid (the oneness of Allah), it should therefore be done with only one finger.