Musnad Ahmad 32:1626

'Affan narrated to us, Khalaf ibn Khalifah narrated to us, Hafs ibn 'Umar narrated to us, from Anas ibn Malik, who said: I was sitting with the Messenger of Allah (peace and blessings of Allah be upon him) in a circle, and a man was standing praying. When he bowed, prostrated, and recited the tashahhud, he said in his supplication: "O Allah, I ask You by the fact that to You belongs all praise, there is no god but You, the Bestower (al-Mannan), O Originator of the heavens and the earth, O Possessor of Majesty and Honor, O Ever-Living, O Sustainer, I ask You." The Prophet (peace and blessings of Allah be upon him) said: "Do you know by what he called upon Allah?" They said: Allah and His Messenger know best. He said: "By the One in Whose hand is my soul, he has called upon Allah by His Greatest Name, which, if He is called by it, He answers, and if He is asked by it, He gives."