בראשית יט:טו פירוש: רש״י, רשב״ם, ספורנו ורד״ק

ויאיצו THEY URGED [LOT] — as the Targum takes it, “they pressed” — i.e. they hurried him.

וכמו השחר עלה, the reason the Torah wrote this verse is seeing that it says in verse 23 that Lot had arrived in Tzoar as the sun had risen, this would have been at least 1-2 hours later than the early dawn described here. In other words, the angels delayed carrying out their mission for a considerable period all out of fondness for Avraham, so that his nephew would not perish in Sodom. [I suppose that seeing that Lot had tarried the whole night he could not now save his livestock and chattels, as the time for this had elapsed. Ed.]

ויאיצו, in order that their destruction should take place at the very moment the sun, their great god, would come forth. (compare Berachot 7)