He reported God's messenger as saying, “When one of you makes supplication he must not say, ‘O God, forgive me if Thou wilt, show mercy to me if Thou wilt, provide for me if Thou wilt’, but must make his request definite, for He does what He wills and there is no one to impose compulsion on Him.”
He reported God’s messenger as. saying, “O God, I have entered into a covenant with Thee which Thou wilt not break. I am only a human being, so when I have injured, reviled, cursed or beaten a believer, make that for him a mercy, a purification and a means by which Thou wilt bring him near to Thee on the day of resurrection.”
He reported God’s messenger as saying, “When one of you makes supplication he must not say, ‘O God, forgive me if Thou wilt, but must be definite and cherish a great desire, for nothing which God gives is burdensome to Him.”
Abu Huraira reported God’s messenger as saying, “Every prophet has a supplication which receives an answer, but whereas every prophet made his supplication in this world, I have kept mine till the day of resurrection to be used in intercession for my people, and if God will, it will reach those of my people who have died without associating anything with God.”
Muslim transmitted it, and Bukhari has a shorter version.
