Takhrij Hadith 1807: "I witnessed 'Ali (may Allah…"

I witnessed 'Ali (may Allah be pleased with him) being brought a mount to ride. When he placed his foot in the stirrup, he said: "Bismillah (In the name of Allah)." When he settled upon its back, he said: "Al-hamdu lillah (Praise be to Allah)." Then he said: "Glory be to the One who has provided this to us, for we could not have done it ourselves, and to our Lord we are indeed returning." Then he said: "Al-hamdu lillah" three times, then he said: "Allahu akbar (Allah is Greatest)" three times, then he said: "Glory be to You, I have wronged myself, so forgive me, for none forgives sins except You." Then he laughed. It was said to him: "O Commander of the Believers, what made you laugh?" He said: "I saw the Prophet (peace and blessings be upon him) do just as I did, and then he laughed. So I said: 'O Messenger of Allah, what made you laugh?' He said: 'Your Lord marvels at His servant when he says: "Forgive me my sins" knowing that none forgives sins besides Me.'"