4 If you refuse to let them go, I will bring locusts into your country tomorrow.

Read Exodus 10:4 Using Other Translations

Else, if thou refuse to let my people go, behold, to morrow will I bring the locusts into thy coast:
For if you refuse to let my people go, behold, tomorrow I will bring locusts into your country,
If you refuse, watch out! For tomorrow I will bring a swarm of locusts on your country.