Musnad Ahmad 27:1405

'Affan narrated to us, Hammad ibn Salamah narrated to us, 'Ali ibn Zayd informed us, from Yahya ibn Ya'mar, who said: I said to Ibn 'Umar: "Indeed, there are men among us who claim that the matter is in their own hands; if they wish, they act, and if they wish, they do not act." He said: "Inform them that I am free of them, and they are free of me." Then he said: Gabriel, peace be upon him, came to the Prophet, peace be upon him, and said: "O Muhammad, what is Islam?" He said: "You worship Allah, associating nothing with Him, establish the prayer, give the zakat, fast Ramadan, and perform the pilgrimage to the House." He said: "If I do that, am I a Muslim?" He said: "Yes." He said: "You have spoken the truth." He said: "What is Ihsan (excellence)?" He said: "That you fear Allah, the Exalted, as if you see Him, for if you do not see Him, He sees you." He said: "If I do that, am I a Muhsin (doer of excellence)?" He said: "Yes." He said: "You have spoken the truth." He said: "What is Iman (faith)?" He said: "That you believe in Allah, His angels, His books, His messengers, the resurrection after death, Paradise, the Fire, and the decree, all of it." He said: "If I do that, am I a Mu'min (believer)?" He said: "Yes." He said: "You have spoken the truth."