Exodus 4:21-23

Complete Jewish Bible

²¹ Adonai said to Moshe, “When you get back to Egypt, make sure that you do before Pharaoh every one of the wonders I have enabled you to do. Nevertheless, I am going to make him hardhearted, and he will refuse to let the people go. ²² Then you are to tell Pharaoh: ‘Adonai says, “Isra’el is my firstborn son. ²³ I have told you to let my son go in order to worship me, but you have refused to let him go. Well, then, I will kill your firstborn son!”’”