What is the name of the Surah in which the verse (Indeed, Allah does not forgive association with Him) is found, and what was the reason for its revelation?

The verse: (Indeed, Allah does not forgive association with Him, but He forgives what is less than that for whom He wills) is repeated twice in Surah An-Nisa (verses 48 and 116). The reason for its revelation, as stated by Al-Qurtubi, is that a man asked the Prophet, peace and blessings be upon him, about shirk (polytheism) after he recited the verse "Indeed, Allah forgives all sins," whereupon this verse was revealed.