Sahih Muslim
The Book Pertaining to the Remembrance of Allah, Supplication, Repentance and Seeking Forgiveness (Kitab Al-Dhikr)
Book Number: 035 / Hadith Number: 6525
Abu Huraira reported Allah's Messenger (may peace be upon him) as say- ing: He who seeks repentance (from the Lord) before the rising of the sun from the west (before the Day of Resurrection), Allah turns to him with Mercy.