Muwatta Malik 201
موطأ مالك#201SahihYahya related to me from Malik from Yahya ibn Said that al-Qasim ibn Muhammad showed them how to sit in the tashahhud, and he kept his right foot vertical and laid his left foot down, and sat on his left haunch not on his foot. Then he said, "Abdullah ibn Abdullah ibn Umar saw me doing this and related to me that his father used to do the same thing
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Salim al-HilaliMauquf Sahih
In-book reference: 3:34