Tafsir of Al-Kahf 18:13-15

{And We increased them in guidance} Through divine success (tawfiq) and steadfastness.

{And We bound upon their hearts} We strengthened them with patience to abandon their homelands and comforts, to flee with their faith to the caves, and we emboldened them to stand by the word of truth and openly profess Islam.

{When they stood} Before the tyrant, Decius, without concern for him when he rebuked them for abandoning the worship of idols.

{And they said, "Our Lord is the Lord of the heavens and the earth; we will never invoke besides Him any deity. We would have certainly spoken, then, an excessive transgression (shatatan)."} A statement of shatat, which is excess in injustice and straying far from the truth—derived from shatta, meaning "to be distant." From this comes the expression "he was excessive (ashtata) in bargaining" and other matters.

{These} (Subject)

{Our people} (Appositive)

{Have taken} (Predicate) This is an informative statement in the sense of a denunciation.

{Why do they not bring for them} Meaning: Why do they not bring for their worship [a clear authority]? The possessive noun is omitted here.

{A clear authority?} This is a rebuke, for bringing authority for the worship of idols is impossible. It is proof of the corruption of blind imitation (taqlid) and that in religion, one must have evidence for it to be valid and established.

{Who has invented about Allah a lie?} By attributing partners to Him.

{And when you have withdrawn from them and that which they worship other than Allah, retreat to the cave. Your Lord will spread for you of His mercy and will prepare for you from your affair facility.}