Tafsir of Al-Hijr 15:68

"He said, 'Indeed, these are my guests'" (Al-Dayf), as we have previously established, is originally an infinitive derived from dafa-hu, and thus it is applied to both the singular and the plural. For this reason, it is grammatically correct to use it as a predicate for "these." Its application to the angels—peace be upon them—is according to his (Lot’s) belief, as they appeared in the guise of guests. It is also said: it is according to the belief of [his people] regarding them.

The use of the emphatic particle (inna) is not to deny their knowledge of this, but to establish their connection to him, to manifest his deep concern for them—peace be upon them—and his readiness to uphold their rights and protect them from harm. That is why he said, "So do not disgrace me."

Meaning: Do not disgrace me in their presence by treating them with harm, such that they would realize I hold no status among you; or, do not disgrace me by the disgrace of my guests, for whoever treats a guest with harm has treated the host with harm. It is said: fadhtuhu fadhan wa fadihatan (I disgraced him, a disgrace) when one reveals of his affairs that which brings him shame. It is also said: "The dawn has fadaha (exposed itself)" when it becomes clear to the people.