(How shall Allah guide a people who disbelieved after their belief…) [3:86].
Abu Bakr al-Harithi informed us> Abu Muhammad ibn Hayyan> Abu Yahya 'Abd al-Rahman ibn Muhammad> Sahl ibn 'Uthman> 'Ali ibn 'Asim> Khalid and Dawud> 'Ikrimah> Ibn 'Abbas who reported that a man from the Helpers renounced his religion and joined the idolaters, and Allah, exalted is He, revealed (shall Allah guide a people who disbelieved after their belief) up to His saying (Save those who afterward repent…) (3:89). His people sent him these verses and when they were read to him, he said: “By Allah, my people are not telling a lie about the Messenger of Allah, Allah bless him and give him peace, nor is the Messenger of Allah, Allah bless him and give him peace, telling a lie about Allah. By Allah, I will believe all three”, and he went back repentant. The Messenger of Allah, Allah bless him and give him peace, accepted his repentance and let him be.
Abu Bakr informed us> Abu Muhammad> Abu Yahya> Sahl> Yahya ibn Abi Za'idah> Dawud ibn Abi Hind> 'Ikrimah> Ibn 'Abbas who said: “A certain man from the Helpers renounced Islam and joined idolatry. He later regretted this and sent to his people to ask the Messenger of Allah, Allah bless him and give him peace, whether his repentance would be accepted since he regrets his apostasy. Allah, exalted is He, revealed (How shall Allah guide a people who disbelieved after their belief) until His saying (Save those who afterward repent). When the man's people sent him these verses, he came back and became Muslim”.
Abu 'Abd al-Rahman ibn Abu Hamid informed us> Abu Bakr ibn Zakariyya> Muhammad ibn 'Abd al-Rahman al-Faqih> Ahmad ibn Sayyar> Musaddid ibn Musarhad> Ja'far ibn Sulayman> Hamid al-A'raj> Mujahid who said: “Al-Harith ibn Suwayd was a Muslim. He was with the Messenger of Allah, Allah bless him and give him peace. But he later renounced Islam and joined his own people. Then Allah, exalted is He, revealed this verse (How shall Allah guide a people who disbelieved after their belief) up to His saying (Save those who afterward repent). A man from amongst his people took these verses and read them to him. Al-Harith said: 'By Allah, I know that you are truthful, and I know that the Messenger of Allah, Allah, bless him and give him peace, is more truthful than you, and Allah, exalted is He, is more truthful than all'. He went back, declared his Islam and became a good Muslim”.
Asbab Al-Nuzul by Al-Wahidi , trans. Mokrane Guezzou