Muwatta Malik 215
موطأ مالك#215SahihYahya related to me from Malik from Nafi that Abdullah ibn Umar, when questioned about forgetfulness in the prayer, said, "If you think that you have forgotten part of the prayer, then pray it
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: 3:48