The Book of Faith (Kitab Al-Iman)
Muslim :: Book 1 : Hadith 396
Abu Zubair heard Jabir b. Abdullah reporting it from the Apostle of Allah (may peace be upon him): For every apostle was a prayer with which he prayed (to his Lord) for his Ummah, but I have reserved my prayer for the intercession of my Ummah on the Day of Resurrection.