From Sahih Muslim (Hadith 6324):
Abu Huraira reported that Allah's Messenger (ﷺ) said to Bilal:Bilal, narrate to me which act at the time of morning prayer you did in Islam for which you hope to receive good reward, for I heard during the night the sound of your steps before me in Paradise. Bilal said: I did not do any act in Islam for which I hope to get any benefit but this that when I perform complete ablution during the night or day I observe prayer with that purification what Allah has ordained for me to pray
Reference: Muslim 6324