“The Lord turned an exceedingly strong west wind, and it carried the locusts, and deposited them into the Red Sea; there did not remain even one locust within the entire border of Egypt. The Lord hardened Pharaoh's heart, and he did not let the children of Israel go” (Exodus 10:19–20). “The Lord turned…a west wind…there did not remain even one locust” – Rabbi Yoḥanan said: When the locusts came, the Egyptians rejoiced.
They said: Let us fill barrels with them. The Holy One blessed be He said: Wicked ones, are you rejoicing over the plague that I brought upon you? Immediately, “the Lord turned an exceedingly strong west [yam] wind”; this is the west [maaravit] wind. “It carried the locusts…” – what is “there did not remain even one locust”?
Even what was salted in the pots and in the barrels flew and went away. “The Lord hardened Pharaoh's heart.”7It is possible that this last line expresses that once Pharaoh saw that even the locusts in the barrels disappeared, he concluded that the plague had been the result of sorcery, as this would not have happened with real locusts. Consequently, he hardened his heart (Etz Yosef).