Exodus 10:19-21

19And Yhwh turned a mighty strong west wind, which took away the locusts, and cast them into the Red sea; there remained not one locust in all the coasts of Egypt.1 20But Yhwh hardened Pharaoh’s heart, so that he would not let the children of Israel go.

21And Yhwh said unto Moses, Stretch out thine hand toward heaven, that there may be darkness over the land of Egypt, even darkness which may be felt.2