"If I were in front of the Messenger of Allah (ﷺ) I would be able to see the whiteness of his armpits." (One of the narrators) Abu Mijlaz said: "It is as if he said that because he was praying."
Sunan an-Nasa'i Book 12, Hadith 79
← Previous Hadith When the Messenger of Allah (ﷺ) prayed he held his arms out so much that the whiteness of his armpits appeared.

Sunan an-Nasa'i Book 12, Hadith 78 Next Hadith → "I prayed with the Messenger of Allah (ﷺ) and I used to see the whiteness of his armpits when he prostrated."

Sunan an-Nasa'i Book 12, Hadith 80