NASAI-KUBRA 1175:
from ʿAbdullāh b. Jaʿfar —
The Messenger of Allah ﷺ said: "Whoever has doubt during his prayer, let him prostrate twice." (One of the narrators) Hajjaj said: "After he has said the taslim." (Another of them) Rawh said: "While he is sitting." (Using translation from Nasāʾī 1251)
الكبرى للنسائي ١١٧٥:
عن عبد الله بن جعفر —
أَنَّ رَسُولَ اللهِ ﷺ قَالَ «مَنْ شَكَّ فِي صَلَاةٍ فَلْيَسْجُدْ سَجْدَتَيْنِ» قَالَ حَجَّاجٌ «بَعْدَمَا يُسَلِّمُ» وَقَالَ رَوْحٌ «وَهُو جَالِسٌ»
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