Hadith 7:99
He reported God’s messenger as saying, “Turn, you people, in repentance to God, for I turn in repentance to Him a hundred times a day.” Muslim transmitted it.
وَعَنْهُ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «يَا أَيُّهَا النَّاسُ تُوبُوا إِلَى اللَّهِ فَإِنِّي أَتُوبُ إِلَيْهِ فِي الْيَوْمِ مائةَ مرِّةٍ» . رَوَاهُ مُسلم
Original Reference: Mishkat al-Masabih 2325