question #3 Sahih Muslim 716, Book 6, Hadith 89 : Why did the Prophet choose to sit in the mosque after performing the prayer upon his return?

The Messenger of Allah (ﷺ) did not come back from the journey but by day in the forenoon, and when he arrived, he went first to the mosque, and having prayed two rak’ahs in it he sat down in it.