Is my understanding of the noble verse, "Allah does not intend to make any difficulty for you, but to purify you and to complete His favor upon you, that you may be grateful," correct in that everything that befalls a person, even disbelief and sin, is by the will of Allah and aims at purification and the completion of His favor through repentance, and does this not contradict the Quran and Sunnah?

The verse, "Allah does not intend to make any difficulty for you, but He intends to purify you and complete His favor upon you, so that you may be grateful," pertains to the believers; it is addressed to believers only and does not include disbelievers. The purpose of Allah's will in this verse is to ease, purify, and complete His favor upon the believers, not to make disobedience or disbelief a means of purification. Interpreters have explained that "difficulty" (haraj) means hardship, and that through this verse, Allah intended purification from impurities and sins, and the completion of His favor by guiding to Islam. Allah's will in the verse is religious and legislative, not cosmic and predestined.