"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." (Using translation from Nasāʾī 4068)
كَانَ رَجُلٌ مِنَ الْأَنْصَارِ أَسْلَمَ ثُمَّ ارْتَدَّ فَلَحِقَ بِالْمُشْرِكِينَ ثُمَّ نَدِمَ فَأَرْسَلَ إِلَى قَوْمِهِ أَنْ سَلُوا رَسُولَ اللَّهِ ﷺ هَلْ لِي مِنْ تَوْبَةٍ؟ قَالَ فَنَزَلَتْ {كَيْفَ يَهْدِي اللَّهُ قَوْمًا كَفَرُوا بَعْدَ إِيمَانِهِمْ} [آل عمران 86] إِلَى قَوْلِهِ {إِلَّا الَّذِينَ تَابُوا مِنْ بَعْدِ ذَلِكَ وَأَصْلَحُوا فَإِنَّ اللَّهَ غَفُورٌ رَحِيمٌ} [آل عمران 89] قَالَ «فَأَرْسَلَ إِلَيْهِ قَوْمُهُ فَأَسْلَمَ»