Musnad Ahmad

Ali bin Rabi’ah says that I once saw Sayyiduna Ali (may Allah be pleased with him) that a riding animal was brought to him for him to mount. When he placed his foot in its stirrup, he said “Bismillah” (In the name of Allah). When he sat on it, he recited this supplication: «اَلْحَمْدُ لِلّٰهِ سُبْحَانَ الَّذِي سَخَّرَ لَنَا هَذَا وَمَا كُنَّا لَهُ مُقْرِنِينَ وَإِنَّا إِلَى رَبِّنَا لَمُنْقَلِبُونَ» “All praise is for Allah. Glory be to Him Who has subjected this (animal) to us, for we could not have subdued it (by ourselves), and surely to our Lord we are returning.” Then he said “Alhamdulillah” (All praise is for Allah) three times and “Allahu Akbar” (Allah is the Greatest) three times, and then said: «سُبْحَانَكَ لَا إِلٰهَ إِلَّا أَنْتَ قَدْ ظَلَمْتُ نَفْسِي فَاغْفِرْ لِي» “O Allah! You are pure, there is no deity except You. I have wronged myself, so forgive me.” Then he smiled. I asked, “O Commander of the Faithful! What made you smile at this moment?” He replied, “I saw the Prophet (peace and blessings be upon him) do as I have done, and he also smiled. I asked him the reason, and he (peace and blessings be upon him) said, ‘When the servant says: O Lord! Forgive me, the Lord is pleased and says: My servant knows that none forgives sins except Me.’”