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 ﷺ, is there any repentance for me?' His people came to the Messenger of Allah ﷺ 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."

أَخْبَرَنَا مُحَمَّدُ بْنُ عَبْدِ اللَّهِ بْنِ بَزِيعٍ، قَالَ حَدَّثَنَا يَزِيدُ، - وَهُوَ ابْنُ زُرَيْعٍ - قَالَ أَنْبَأَنَا دَاوُدُ، عَنْ عِكْرِمَةَ، عَنِ ابْنِ عَبَّاسٍ، قَالَ كَانَ رَجُلٌ مِنَ الأَنْصَارِ أَسْلَمَ ثُمَّ ارْتَدَّ وَلَحِقَ بِالشِّرْكِ ثُمَّ تَنَدَّمَ فَأَرْسَلَ إِلَى قَوْمِهِ سَلُوا لِي رَسُولَ اللَّهِ ﷺ هَلْ لِي مِنْ تَوْبَةٍ فَجَاءَ قَوْمُهُ إِلَى رَسُولِ اللَّهِ ﷺ فَقَالُوا إِنَّ فُلاَنًا قَدْ نَدِمَ وَإِنَّهُ أَمَرَنَا أَنْ نَسْأَلَكَ هَلْ لَهُ مِنْ تَوْبَةٍ فَنَزَلَتْ { كَيْفَ يَهْدِي اللَّهُ قَوْمًا كَفَرُوا بَعْدَ إِيمَانِهِمْ } إِلَى قَوْلِهِ { غَفُورٌ رَحِيمٌ } " . فَأَرْسَلَ إِلَيْهِ فَأَسْلَمَ .