(And those who put away false gods lest they should worship them…) [39:17].
Ibn Zayd said: “This verse was revealed about three people who confessed the oneness of Allah in the pre-Islamic period: Zayd ibn ‘Amr, Abu Dharr al-Ghifari and Salman al-Farisi”.
(… for them there are glad tidings. Therefor give good tidings (O Muhammad) to My bondmen who hear advice and follow the best thereof…) [39:17-18].
‘Ata’ reported that Ibn ‘Abbas said: “When Abu Bakr al-Siddiq believed in the Prophet, Allah bless him and give him peace, and followed him, ‘Uthman, ‘Abd al-Rahman ibn ‘Awf, Talhah, al-Zubayr, Sa‘id ibn Zayd, Sa‘d ibn Abi Waqqas went to him and asked him [whether he believed in the Prophet]. He informed them about his faith and they believed [with him on the spot]. Allah revealed about them (Therefor give good tidings (O Muhammad) to My bondmen who hear advice) i.e. from Abu Bakr (and follow the best thereof)”.
Asbab Al-Nuzul by Al-Wahidi , trans. Mokrane Guezzou