And His statement: “Those who prevailed in the matter said, ‘We shall certainly build over them a place of worship.’” [18:21]

those who prevailed in their matter: that is, those who controlled the affair of the People of the Cave—the people of authority and influence.

We shall certainly build over them: around them.

a place of worship: a site where prayers would be offered; people would visit them and seek blessing through them.

Overall meaning of the verse: Allah, in a tone of censure, relates that the authorities who managed the affair of the People of the Cave declared, “We will erect around them a place of prayer to which people will come and seek blessing through them.”

Relevance of the verse to the chapter: it serves as evidence that members of this community will likewise build mosques over graves, just as those before them did.

Points derived from the verse:

1. Building mosques over graves is forbidden and one must beware of it, for it leads to shirk (associating partners with Allah).
2. There will be people in this nation who construct mosques over graves, repeating what previous communities did.
3. A warning against exaggerating the status of the righteous.
4. Erecting mosques over graves constitutes such exaggeration.