Musnad Ahmad 30:1080

The Messenger of Allah, may Allah bless him and grant him peace, said: "O Allah, I take a covenant with You that You will not break. I am only a human being, so whichever of the believers I have harmed, or insulted, or lashed, or cursed, make it for him a prayer, a purification, and a means of nearness by which You bring him near to You on the Day of Resurrection."