Clark on Matthew 24 verses 21 and 29
Verse 21
For then shall be great tribulation - No history can furnish us with a parallel to the calamities and miseries of the Jews: - rapine, murder, famine, and pestilence within: fire and sword, and all the horrors of war, without. Our Lord wept at the foresight of these calamities; and it is almost impossible for any humane person to read the relation of them in Josephus without weeping also. St. Luke, Luke 21:22, calls these the days of vengeance, that all things which were written might be fulfilled.
Verse 29
Immediately after the tribulation, etc. - Commentators generally understand this, and what follows, of the end of the world and Christ's coming to judgment: but the word immediately shows that our Lord is not speaking of any distant event, but of something immediately consequent on calamities already predicted: and that must be the destruction of Jerusalem.