Sahih Muslim
The Book of Faith (Kitab Al-Iman)
Book Number: 001 / Hadith Number: 390
Abu Huraira said: The Messenger of Allah (may peace be upon him) said: Every Messenger is endowed with a prayer which is granted and by which he would (pray to his Lord) and it would he granted for him. I have, however, reserved my prayer for the intercession of my Ummab on the Day of Resurrection.