Exodus 9:35
The heart of Pharaoh was hardened, and he didn't let the children of Israel go, just as Yahweh had spoken through Moses.
Exodus 4:21
Yahweh said to Moses, "When you go back into Egypt, see that you do before Pharaoh all the wonders which I have put in your hand, but I will harden his heart and he will not let the people go.
Treasury of Scripture Knowledge
Summary
And the heart of Pharaoh was hardened, neither would he let the children of Israel go; as the LORD had spoken by Moses.
General references
Bible References
General references
Jeremiah 34:11
but afterwards they turned, and caused the servants and the handmaids, whom they had let go free, to return, and brought them into subjection for servants and for handmaids.