Exodus 4:21-23 ▼

21 And YHWH says to Moses, “In your going to return to Egypt, see—all the wonders which I have put in your hand—that you have done them before Pharaoh, and I strengthen his heart, and he does not send the people away;

22 and you have said to Pharaoh, Thus said YHWH: My son, My firstborn [is] Israel,

23 and I say to you, send My son away, and he serves Me; and [if] you refuse to send him away, behold, I am slaying your son, your firstborn.”