Sunan an-Nasa'i 4068

It was narrated that Ibn 'Abbas said:"A man from among the Ansar accepted Islam, then he apostatized and went back to Shirk. Then he regretted that, and sent word to his people (saying): 'Ask the Messenger of Allah [SAW], is there any repentance for me?' His people came to the Messenger of Allah [SAW] and said: 'So and so regrets (what he did), and he has told us to ask you if there is any repentance for him?' Then the Verses: 'How shall Allah guide a people who disbelieved after their Belief up to His saying: Verily, Allah is Oft-Forgiving, Most Merciful' was revealed. So he sent word to him, and he accepted Islam