"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 وَلَحِقَ بِالشِّرْكِ ثُمَّ نَدِمَ فَأَرْسَلَ إِلَى قَوْمِهِ سَلُوا لِي رَسُولَ اللهِ ﷺ هَلْ لِي مِنْ تَوْبَةٍ فَجَاءَ قَوْمُهُ إِلَى رَسُولِ اللهِ ﷺ فَقَالُوا إِنَّ فُلَانًا نَدِمَ وَإِنَّهُ أَمَرَنَا أَنْ نَسْأَلَكَ هَلْ لَهُ مِنْ تَوْبَةٍ فَنَزَلَتْ {كَيْفَ يَهْدِي اللهُ قَوْمًا كَفَرُوا بَعْدَ إِيمَانِهِمْ} [آل عمران 86] إِلَى قَوْلِهِ {غَفُورٌ رَحِيمٌ} [البقرة 173] فَأَرْسَلَ إِلَيْهِ فَأَسْلَمَ  

"Whoever disbelieved in Allah after his belief, except him who is forced thereto and whose heart is at rest with Faith; but such as open their breasts to disbelief, on them is wrath from Allah, and theirs will be a great torment." "This was abrogated, and an exception was made, as Allah said: "Then, verily, your Lord for those who emigrated after they had been put to trials and thereafter strove hard and fought (for the Cause of Allah) and were patient, verily, your Lord afterward is, Oft-Forgiving, Most Merciful." This was 'Abdullah bin Sa'd bin Abi As-Sarh who was the governor of Egypt and used to write to the Messenger of Allah [SAW]. The Shaitan misled him and he went and joined the unbelievers. So he (the Prophet [SAW]) commanded that he be killed on the day of the Conquest of Makkah. Then, 'Uthman bin 'Afan sought protection for him, and the Messenger of Allah [SAW] granted him protection." (Using translation from Nasāʾī 4069)  

فِي سُورَةِ النَّحْلِ {مَنْ كَفَرَ بِاللهِ مِنْ بَعْدِ إِيمَانِهِ إِلَّا مَنْ أُكْرِهَ} [النحل 106] إِلَى {وَلَهُمْ عَذَابٌ عَظِيمٌ} [النحل 106] فَنُسِخَ وَاسْتُثْنِيَ مِنْ ذَلِكَ فَقَالَ {ثُمَّ إِنَّ رَبَّكَ لِلَّذِينَ هَاجَرُوا مِنْ بَعْدِ مَا فُتِنُوا ثُمَّ جَاهَدُوا وَصَبَرُوا إِنَّ رَبَّكَ مِنْ بَعْدِهَا لَغَفُورٌ رَحِيمٌ} [النحل 110] وَهُوَ عَبْدُ اللهِ بْنُ سَعْدِ بْنِ أَبِي سَرْحٍ الَّذِي كَانَ عَلَى مِصْرَ كَانَ يَكْتُبُ لِرَسُولِ اللهِ ﷺ فَأَزَلَّهُ الشَّيْطَانُ فَلَحِقَ بِالْكُفَّارِ فَأَمَرَ بِهِ أَنْ يُقْتَلَ يَوْمَ الْفَتْحِ وَاسْتَجَارَ لَهُ عُثْمَانُ بْنُ عَفَّانَ فَأَجَارَهُ رَسُولُ اللهِ ﷺ