Sahih Muslim, Chapter: Faith (Kitab Al Iman)

The Prophet of Allah (may peace be upon him) 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.