Verses 21-29 “21And the LORD 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.
22And Moses stretched forth his hand toward heaven; and there was a thick darkness in all the land of Egypt three days:
23They saw not one another, neither rose any from his place for three days: but all the children of Israel had light in their dwellings.
24And Pharaoh called unto Moses, and said, Go ye, serve the LORD; only let your flocks and your herds be stayed: let your little ones also go with you.
25And Moses said, Thou must give us also sacrifices and burnt offerings, that we may sacrifice unto the LORD our God.
26Our cattle also shall go with us; there shall not an hoof be left behind; for thereof must we take to serve the LORD our God; and we know not with what we must serve the LORD, until we come thither.
27But the LORD hardened Pharaoh’s heart, and he would not let them go.
28And Pharaoh said unto him, Get thee from me, take heed to thyself, see my face no more; for in that day thou seest my face thou shalt die.
29And Moses said, Thou hast spoken well, I will see thy face again no more.”

The “thick darkness” of the ninth plague reminds us of God’s use of light and darkness to illustrate evil vs. righteousness and hell vs. heaven. Those who reject Christ will suffer far worse than any of the people of Egypt suffered in all of these plagues (not for three days only v.22, but for all eternity). It should be noted that Moses refused to compromise at all with Pharaoh; no, not so much as leaving one hoof behind (vv24-26)! Moses was uncompromising because he knew God’s standard, and he also knew how everything was going to turn out. There is no need to compromise when you know that you are on the winning side.