Abu Dawood: Hadith 2603

Ali ibn Rabi'ah said: I was present with Ali while a beast was brought to him to ride. When he put his foot in the stirrup, he said: "In the name of Allah." Then when he sat on its back, he said: "Praise be to Allah." He then said: "Glory be to Him Who has made this subservient to us, for we had not the strength, and to our Lord do we return." He then said: "Praise be to Allah (thrice); Allah is Most Great (thrice): glory be to You, I have wronged myself, so forgive me, for only You forgivest sins." He then laughed. He was asked: At what did you laugh? He replied: I saw the Messenger of Allah (ﷺ) do as I have done, and laugh after that. I asked: Messenger of Allah , at what are you laughing? He replied: Your Lord, Most High, is pleased with His servant when he says: "Forgive me my sins." He know that no one forgives sins except Him.