Exodus 4:21-24

²¹ And the Lord said to Moses, When you go back to Egypt, see that you do before Pharaoh all the wonders which I have given you power to do: but I will make his heart hard and he will not let the people go. ²² And you are to say to Pharaoh, The Lord says, Israel is the first of my sons: ²³ And I said to you, Let my son go, so that he may give me worship; and you did not let him go: so now I will put the first of your sons to death.

²⁴ Now on the journey, at the night's resting-place, the Lord came in his way and would have put him to death.