question #3 Sahih Muslim 497b, Book 4, Hadith 271 : What can be inferred about the Prophet’s (ﷺ) prayer from the visibility of his armpits during prostration?

When the Messenger of Allah (ﷺ) prostrated, he kept his hands so much apart from each other that when it was seen from behind the armpits became visible. Waki’ said: That is their whiteness.