10:18: And Moses going forth from the presence of Pharao, prayed to the Lord:
10:19. And he made a very strong wind to blow from the west, and it took the locusts and cast them into the Red Sea: there remained not so much as one in all the coasts of Egypt.
10:20. And the Lord hardened Pharao's heart, neither did he let the children of Israel go.
10:21. And the Lord said to Moses: Stretch out thy hand towards heaven: and may there be darkness upon the land of Egypt so thick that it may be felt.
Darkness upon the land of Egypt, so thick that it may be felt... By means of the gross exhalations, which were to cause and accompany the darkness.
10:22. And Moses stretched forth his hand towards heaven: and there came horrible darkness in all the land of Egypt for three days.
10:23. No man saw his brother, nor moved himself out of the place where he was: but wheresoever the children of Israel dwelt, there was light.
10:24. And Pharao called Moses and Aaron, and said to them: Go, sacrifice to the Lord: let your sheep only, and herds remain, let your children go with you.
10:25. Moses said: Thou shalt give us also sacrifices and burnt- offerings, to the Lord our God.
10:26. All the flocks shall go with us; there shall not a hoof remain of them: for they are necessary for the service of the Lord our God: especially as we know not what must be offered, till we come to the very place.