question #1 Sahih Muslim 497a, Book 4, Hadith 270 : What is the significance of the Prophet’s posture during prostration in prayer?

When the Messenger of Allah (ﷺ) prostrated himself, he spread his arms, i. e. he separated them so much that the whiteness of his armpits became visible from behind and when he sat (for Jalsa) he rested on his left thigh.