Musnad Ahmad 1018:50

Muhammad ibn Ja‘far narrated to us, Shu‘bah narrated to us, he said: I heard Abu ‘Aqil narrating from Sabiq ibn Najiyah, from Abu Salam, who said: We were sitting in the mosque of Homs when a man passed by, and they said: "This is a servant of the Messenger of Allah, peace and blessings of Allah be upon him." He said: So I stood up and asked him, and I said: "Narrate to us what you heard from the Messenger of Allah, peace and blessings of Allah be upon him, that has not been circulated among men between you two." He said: I heard the Messenger of Allah, peace and blessings of Allah be upon him, saying: "There is no Muslim servant who says three times when he reaches the evening or the morning: 'I am pleased with Allah as a Lord, with Islam as a religion, and with Muhammad as a Prophet,' except that it is a duty upon Allah to please him on the Day of Resurrection."