Tafsir of Al-Kahf 18:30-31

{أولئك} is the predicate of inna (in verse 30), and {إنا لا نضيع} is a parenthetical clause. You may also consider both {إنا لا نضيع} and {أولئك} as two predicates together, or consider {أولئك} as a new sentence (inchoative) serving as an explanation for the vague reward mentioned previously.

If you ask: If you make {إنا لا نضيع} the predicate, where is the pronoun referring back to the subject? I say: {من أحسن عملا} (whoever does good deeds) and {الذين آمنوا وعملوا الصالحات} (those who believe and do righteous deeds) are bound by a single meaning; thus, {من أحسن} stands in the place of the pronoun. Or, if you intended: "Whoever among them does good deeds," it is like saying: "Clarified butter is two manns for a dirham."

The first {من} is for the beginning of the sentence, and the second is for clarification. The indefiniteness of {أساور} (bracelets) is to emphasize the ambiguity of their excellence.

He combined {سندس}—which is the thin variety of silk—with {إستبرق}—which is the thick variety—to encompass both types. He specified reclining {متكئين} because it is the posture of those living in luxury and kings upon their thrones.

{واضرب لهم مثلا رجلين جعلنا لأحدهما جنتين من أعناب وحففناهما بنخل وجعلنا بينهما زرعا * كلتا الجنتين آتت أكلها ولم تظلم منه شيئا وفجرنا خلالهما نهرا * وكان له ثمر فقال لصاحبه وهو يحاوره أنا أكثر منك مالا وأعز نفرا}

(And present to them an example of two men: We granted to one of them two gardens of grapevines, and We bordered them with palm trees and placed between them [fields of] crops. Each of the two gardens brought forth its fruit and did not fall short thereof in anything. And We caused to gush forth within them a river. And he had fruit, so he said to his companion while he was conversing with him, "I am greater than you in wealth and mightier in [number of] men.")