Musnad Ahmad 32:1338

Ja'far ibn 'Awn narrated to us, he said: Mis'ar informed us, from Qatadah, from Anas, that the Messenger of Allah, peace and blessings of Allah be upon him, said: "Indeed, for every prophet there is a supplication with which he supplicated for his nation, and I have reserved my supplication as an intercession for my nation on the Day of Resurrection."