Jami` at-Tirmidhi 294
جامع الترمذي#294SahihIbn Umar narrated:"When the Prophet would sit during the Salat, he would place his right hand on his knee, and raise his finger, the one that is next to the [right] thumb, supplicating with it, and his left hand was spread flat on his left knee
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Ahmad Muhammad ShakirSahih
Al-AlbaniSahih
Zubair Ali ZaiSahih Muslim
In-book reference: 2:146