John Lightfoot on Matthew 24:22

[Those days shall be shortened.] God lengthened the time for the sake of the elect, before the destruction of the city; and in the destruction, for their sakes he shortened it. Compare with these words before us 2 Peter 3:9, "The Lord is not slack concerning his promise," &c. It was certainly very hard with the elect that were inhabitants of the city, who underwent all kinds of misery with the besieged, where the plague and sword raged so violently that there were not living enough to bury the dead; and the famine was so great, that a mother ate her son (perhaps the wife of Doeg Ben Joseph, of whom see such a story in Babyl. Joma). And it was also hard enough with those elect who fled to the mountains, being driven out of house, living in the open air, and wanting necessaries for food: their merciful God and Father, therefore, took care of them, shortening the time of their misery, and cutting off the reprobates with a speedier destruction; lest, if their stroke had been longer continued, the elect should too far have partaken of their misery.

The Rabbins dream that God shortened the day on which wicked king Ahab died, and that ten hours; lest he should have been honoured with mourning.