It was narrated from Ibn ‘Umar that the Prophet (ﷺ) used to sit during prayer, putting his hands on his knees and raising his right finger which was next to his thumb, supplicating with it, and with his left hand (spread out) on his knee
Hadith No. 913
Sunan Ibn Majah
Gradings:
Al-Albani:
Sahih
Muhammad Fouad Abd al-Baqi:
Sahih
Shuaib Al Arnaut:
Sahih
Zubair Ali Zai:
Sahih Muslim