Barnes New Testament Notes

Verse 27. For as the lightning cometh out of the east, etc. This is not designed to denote the quarter from which he would come, but the manner. He does not mean to affirm that the Son of man will come from the east, but that he will come in a rapid and unexpected manner, like the lightning. Many would be looking for him in the desert; many in secret places. But, he said, it would be useless to be looking in that manner. It was useless to look to any particular part of the heavens, to know where the lightning would next flash. In a moment it would blaze in an unexpected part of the heavens, and shine at once to the other part. So rapidly, so unexpectedly, in so unlooked-for a quarter would be his coming. See Lu 10:18; Zec 9:14.

The coming of the Son of man. It has been doubted whether this refers to the destruction of Jerusalem, or to the coming at the day of judgment. For the solution of this doubt, let it be remarked,

(1.) that those two events are the principal scenes in which our Lord said he would come, either in person or in judgment.

(2.) That the destruction of Jerusalem is described as his coming, his act, for their great crimes.

(3.) That these events -- the judgment of Jerusalem and the final judgment -- in many respects greatly resemble each other.

(4.) That they will bear, therefore, to be described in the same language. And,

(5.) therefore, that the same words often include both events, as properly described by them. The words, therefore, had doubtless a primary reference to the destruction of Jerusalem, but such an amplitude of meaning as also to express his coming to judgment.

See Barnes "Isa 1:1, § 7, (3.)

{y} "the lightning" Zec 9:14; Lu 17:24