Sahih Muslim Book 35, Hadith Number 6522.
Chapter : Excellence of seeking forgiveness from Allah and seeking that very much.
Al-Agharr al-Muzani, who was one amongst the Companions (of the Holy Prophet) reported that Allah’s Messenger (may peace be upon him) said: There is (at times) some sort of shade upon my heart, and I seek forgiveness from Allah a hundred times a day.