التفسير التبليغي
(He (Abraham) said, "What then is your errand, O messengers?" (51:31))
He followed his story with the story of Lot, his nephew, peace be upon him.
(He said) meaning Abraham, peace be upon him, when he realized that they were angels sent for a purpose.
He asked them after he had hosted them, following the tradition of hospitality, which dictates that a guest should not be asked about the purpose that brought him to that dwelling until he is ready to depart.
(He said, "What then is your errand, O messengers?") This is from the etiquette of hospitality; if a guest hastens to leave, one might ask him, "What is this haste?"
(What then is your errand?) meaning, what is your important matter for which you have been sent, besides the good tidings? (O messengers).
This verse is a warning to the Prophet, peace be upon him, that if his people persist in their error, what befell the people of Lot will befall them.
It is a reminder to humanity of what was done to the nations before them.
Source: التفسير التبليغي