Matthew 24:21-22

For then the tribulation will be great, such as never was from the beginning of the world, and never more shall be.

Mark 13:19

For these days shall bring tribulation, such as the like hath never been from the beginning of the creation which God created unto this time, and never shall be more.

Acts 2:20

The sun shall be turned into darkness, and the moon into blood, before the great and illustrious day of the Lord come.

Romans 11:26

And so all Israel shall be saved: as it is written, "The Deliverer shall go forth out of Sion, and shalt turn away ungodliness from Jacob;

Revelation 6:17

for the great day of his wrath is come, and who is able to stand?

Treasury of Scripture Knowledge

Summary

Alas! for that day is great, so that none is like it: it is even the time of Jacob's trouble; but he shall be saved out of it.

Bible References

For

Acts 2:20
The sun shall be turned into darkness, and the moon into blood, before the great and illustrious day of the Lord come.
Revelation 6:17
for the great day of his wrath is come, and who is able to stand?

So

Matthew 24:21
For then the tribulation will be great, such as never was from the beginning of the world, and never more shall be.
Mark 13:19
For these days shall bring tribulation, such as the like hath never been from the beginning of the creation which God created unto this time, and never shall be more.

But

Romans 11:26
And so all Israel shall be saved: as it is written, "The Deliverer shall go forth out of Sion, and shalt turn away ungodliness from Jacob;