Matthew 24:21-22

for then will be great tribulation, such as has not happened from the beginning of the world until now; no, nor ever shall be.

Mark 13:19

for those days will be a time of tribulation, such as there has not been the like from the beginning of the creation which God created until now, and never will be.

Acts 2:20

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

Romans 11:26

and so all Israel shall be saved; even as it has been written, "There will come out of Zion the Deliverer; He will turn away ungodliness from Jacob;

Revelation 6:17

because the great day of their wrath came, 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 notable day of the Lord come.
Revelation 6:17
because the great day of their wrath came, and who is able to stand?"

So

Matthew 24:21
for then will be great tribulation, such as has not happened from the beginning of the world until now; no, nor ever shall be.
Mark 13:19
for those days will be a time of tribulation, such as there has not been the like from the beginning of the creation which God created until now, and never will be.

But

Romans 11:26
and so all Israel shall be saved; even as it has been written, "There will come out of Zion the Deliverer; He will turn away ungodliness from Jacob;