Mark 13:20
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. 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.
On the Mount of Olives Peter and James and John and Andrew asked when these things shall be and what shall be the sign when all shall be fulfilled concerning the destruction of the temple, and this is part of Jesus' answer to them. Within that answer it comes after the warning to flee to the mountains when the abomination of desolation stands where it ought not, and before the warning against false Christs and false prophets, the darkening of the sun and moon and falling of the stars, and the coming of the Son of man in the clouds to gather His elect. It teaches that in those days shall be affliction such as was not from the beginning of the creation unto this time, neither shall be, and except 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.
The discourse mingles the destruction of Jerusalem with the great day of Christ's coming and the end of the world, mercifully blending the two great crises because the disciples could not have endured the future events if opened to them separately as Christ beheld them, leaving them to study out the meaning for themselves. What was spoken about Jerusalem reaches beyond that event to the final conflagration when the Lord rises out of His place to punish the world for iniquity, and the whole discourse was given not for the disciples only but for those who live in the last scenes of this earth's history. The warning is connected with the destruction of sinful cities by earthquakes, fire, and flood, showing that God by His authority can bring human schemes to an end and destroy even carefully protected, magnificent possessions. The Lord limits the time of suffering, and His soon return will put an end to Satan's cruel work, without which the earth would eventually be depopulated.