He who repents before the sun rises from the west, Allah will forgive him

 - وعن أبي هريرة رضي الله عنه قال قال رسول الله صلى الله عليه و سلم : [ من تاب قبل أن تطلع الشمس من مغربها تاب الله عليه ] رواه مسلم .

 

Abu Hurairah (May Allah be pleased with him) narrated: Messenger of Allah (PBUH) said, "He who repents before the sun rises from the west, Allah will forgive him".
[Muslim].

Commentary:

 Taubah means returning to Allah from sins. When a person commits a sin, he goes away from Allah. When he repents, he returns to Allah and desires for being pardoned by Him, and getting near Him. This returning towards Him is Taubah. When it is said that `Allah turns towards him', it means that Allah accepts his repentance.