Translation:

18. (Both) the Jews and the Christians say: "We are sons of Allah and His beloved." Say: "Why then doth He punish you for your sins? Nay ye are but men of the men He hath created: He forgiveth whom He pleaseth and He punisheth whom He pleaseth: and to Allah belongeth the dominion of the heavens and the earth and all that is between: and unto Him is the final goal (of all)."

Notes (Tafseer)

718. Sons of God: Cf. Job, xxxviii. 7; "When the morning stars sang together, and all the sons of God shouted for joy." In the 29th Psalm, 1st verse, the authorised Translation "O ye mighty" should apparently be "O ye sons of Elim". El being a name of God, Cf. also Genesis, vi. 2: "The sons of God saw the daughters of men." Beloved: Cf. Psalms, cxxvii, 2: "He giveth his beloved sleep." If used figuratively, these and like words refer to the love of Allah. Unfortunately, "son" used in a physical sense, or "beloved" in an exclusive sense as if Allah loved only the Jews, make a mockery of religion.

719. This refrain in the last verse negatives the idea of sonship, and in this verse negatives the idea of an exclusive "Beloved". In both cases it means that Allah is independent of physical relationship or exclusive partiality,