question #1 Sahih Muslim 199a, Book 1, Hadith 397 : What is the significance of the reserved prayer of the Prophet Muhammad (ﷺ) for his Ummah on the Day of Resurrection?

The Prophet of Allah (ﷺ) said: There is for every apostle a prayer which is granted, but every prophet showed haste in his prayer. I have, however, reserved my prayer for the intercession of my Ummah on the Day of Resurrection, and it would be granted, if Allah so willed, in case of everyone amongst my Ummah provided he dies without associating anything with Allah.