(He it is Who blesseth you, and His angels…) [33:43]. Mujahid said: “When the verse (Lo! Allah and His angels shower blessings on the Prophet) [33:56], Abu Bakr said: ‘Allah, exalted is He, has not given you any good except that made us partake of it’. Then, this verse (Lo! Allah and His angels shower blessings on the Prophet) was revealed”.
Asbab Al-Nuzul by Al-Wahidi , trans. Mokrane Guezzou
