Exodus 10:20-22

American Standard Version

²⁰ But Jehovah ^[a]hardened Pharaoh’s heart, and he did not let the children of Israel go.

²¹ And Jehovah said unto Moses, Stretch out thy hand toward heaven, that there may be darkness over the land of Egypt, ^[b]even darkness which may be felt. ²² And Moses stretched forth his hand toward heaven; and there was a thick darkness in all the land of Egypt three days;