Sunan an-Nasa'i 1106
سنن النسائي#1106SahihIt was narrated from Abdullah bin Malik bin Buhainah that:When the Messenger of Allah (ﷺ) prayed he held his arms out so much that the whiteness of his armpits appeared
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Abu GhuddahSahih
Al-AlbaniSahih
Zubair Ali ZaiSahih - Agreed Upon
In-book reference: 12:78