I will defer to Bro. Ralph Woodrow for the explanation:
Matthew: “For then shall be great tribulation, such as was not since the beginning of the world to this time, no, nor ever shall be. And except those days should be shortened, there should no flesh be saved: but for the elect’s sake those days shall be shortened” (24:21, 22).
Mark: “For in those days shall be affliction, such as was not from the beginning of the creation which God created unto this time, neither shall be. And except that the Lord had shortened those days, no flesh should be saved: but for the elect’s sake, whom he hath chosen, he hath shortened the days” (13:19, 20).
Luke: “For these be the days of vengeance, that all things which are written may be fulfilled . . . for there shall be great distress in the land, and wrath upon this people. And they shall fall by the edge of the sword, and shall be led away captive into all nations: and Jerusalem shall be trodden down of the Gentiles” (21:22-24).
"The prophecy that Jesus gave continues with these words: “And except those days should be shortened, there should no flesh be saved [alive]; but for the elect’s sake those days shall be shortened” (Mt. 24:22; Mk. 13:20).
We must bear in mind that the reference here is to the area upon which the tribulation of those days fell — Judea and Jerusalem. It should not be wrested from its proper setting.
Concerning the destruction that came upon this
same land and city in the Old Testament, we read: “Your country is desolate, your cities are burned with fire: your land strangers devour it in your presence, and it is desolate . . . Except the Lord of hosts had left unto us a very small remnant, we should have been as Sodom, and we should have been like unto Gomorrah” (Isaiah 1:1, 7, 9). With the cities of Sodom and Gomorrah, of course, there was no flesh saved alive. It was
total destruction.
There is an obvious
similarity here. In the Old Testament, “Except the Lord” had left a remnant, no flesh would have been saved alive. In the New Testament, “Except the Lord” had shortened the days, there would no flesh be saved alive. The meaning is basically the same in both cases.
We will notice in more detail later that the destruction that came upon that land and people was the judgment of
God. It was no mere accident that things happened the way they did. The tribulation had
definite bounds, however; it could only continue for a limited period of time. The days, we are plainly told, had been
shortened. The Gentile armies could only go so far!
Looking at Luke’s account of “the days of vengeance” and “great distress in the land, and wrath upon this people”, we read: “Jerusalem shall be trodden down of the Gentiles.” Now, who were the Gentiles that did this? It was
Titus and his armies. And how long were they to tread it down? “Until the times of the Gentiles [Titus and his armies] be fulfilled” (Lk. 21:24). In other words, only a certain length of time was allotted for them to carry out the work of judgment; or, as Matthew and Mark put it, the days had been shortened!
Some have pulled these five words, “The times of the Gentiles”, out of their setting and have attempted to stretch them into a long
age of time for which there is no real proof in this passage. One noted writer of the dispensational school says: “`the times of the Gentiles’ covers the entire period during which the nation of the Jews, the city of Jerusalem, and the land of Palestine are under Gentile domination. This began with Nebuchadnezzar’s conquest of Palestine and will end at the Revelation of the Lord Jesus Christ from heaven at the close of the Great Tribulation.”2 This is the teaching set forth in the notes of the
Scofield Bible.3
But considering the setting, this verse about “the times of the Gentiles” is not talking about who is
ruling Jerusalem, it is talking about Jerusalem being
trodden down. It is not talking about long ages of time, but of Jerusalem being trodden down by Gentiles, the Gentiles being those that destroyed it in 70 A.D. — Titus and his armies!
It was no exaggeration when Jesus spoke about no flesh being saved alive in that land upon which his judgment came. Josephus informs us that “the populace was almost annihilated . . . there was no part of Judea, which did not partake of the calamities of the capital city.” But for the elect’s sake, those days were shortened; the times allotted the Gentile armies to inflict that tribulation were limited. Though the Christians had escaped into the mountains, living without housing or provisions, they too could have eventually been destroyed by sword or famine if those days of tribulation had not been shortened."