Why does God sometimes tell Moses to "go to Pharaoh" (lekh el Par'oh) and other times to "come to Pharaoh" (bo el Par'oh)? Rabbi Levi Yitzchak of Berditchev discovers two entirely different types of miracles hidden in this subtle shift.
The first type of miracle punishes the oppressor and forces them to stop. The second type is far more radical: it transforms the oppressor's heart entirely, turning an enemy into an ally. The Purim story illustrates the second type. Haman was punished and destroyed. But Achashverosh was not destroyed. God changed his heart, and he became friendly to the Jews.
When God says "come" (bo) to Pharaoh rather than "go" (lekh), the nuance is not confrontational but invitational. God is giving Pharaoh a chance to turn over a new leaf. The phrase "I have hardened his heart" (Exodus 10:1) is read by Rabbi Levi Yitzchak not as a punishment but as a sign that God has taken control of Pharaoh's heart, the way He took control of Achashverosh's.
The plague of the firstborn on the night of Passover was the culmination of both types. According to Sh'mot Rabbah 9:12, each plague lasted about a month, with one week after the warning for the Egyptians to repent. The plague of hail fell in the first half of Shevat. The killing of the firstborn occurred in mid-Nisan. Each plague was both a punishment and an invitation.
The Talmud (Sotah 11) teaches that God repays sinners measure for measure but rewards the righteous in excess of their merits. If Pharaoh had responded to the invitation hidden within "come," if he had changed his heart the way Achashverosh later would, the night of the firstborn might have been the night of Pharaoh's redemption. Instead, it became the night that made the Exodus necessary.