1 Corinthians 10:8

Let us not practice immorality, like some of them, twenty-three thousand of whom fell dead in one day,

Hebrews 2:2-3

For if the message delivered by angels proved to be authentic, and every violation or neglect of it led to a corresponding penalty,

Treasury of Scripture Knowledge

Summary

And the children of Levi did according to the word of Moses: and there fell of the people that day about three thousand men.

Bible References

There fell

1 Corinthians 10:8
Let us not practice immorality, like some of them, twenty-three thousand of whom fell dead in one day,
Hebrews 2:2
For if the message delivered by angels proved to be authentic, and every violation or neglect of it led to a corresponding penalty,