Moshe’s greatness and Pharaoh’s stubbornness[1]
ואמרת אליו וגו’ שלח את עמי במדבר והנה לא שמעת עד כה
You shall tell [Pharaoh]: “…Send out my people to the wilderness. Behold, you haven’t listened until ‘koh’”[2]
Just as the Ten Plagues were about to begin, Hashem commanded Moshe to send a message to Pharaoh: “You have been impudent until now. I have commanded you to send out My people from Egypt, and you have refused. You will know that I am G-d through the Ten Plagues. Then you will send out My people”. This is the simple understanding of the verse, which says you, Pharaoh, haven’t listened until כה (until now)[3]. However, the Midrashic understanding[4] is Pharaoh, you will not listen to me to send them out until you hear the word “כה” (literally: thus). Before the final plague, the death of the firstborns, Moshe warned Pharaoh: כה אמר יקוק, כחצות הלילה אני יוצא בתוך מצרים ומות כל בכור…, “Thus says Hashem: ‘Around midnight I will go out within Egypt, and all the firstborn shall die …’”[5]. Moshe told Pharaoh only then will you send them out.