“I have taken the Levites instead of all the firstborn of the children of Israel. And I have given the Levites as a gift to Aaron and his sons from among the children of Israel, to do the work for the children of Israel in the tabernacle of meeting, and to make atonement for the children of Israel, that there be no plague among the children of Israel when the children of Israel come near the sanctuary” (Numbers 8:18-19).
To consecrate or to sanctify someone is the idea of separation. That person has been set aside for a purpose. When God kept all of the firstborn of Israel from being killed by the angel that passed over during the tenth plague, He redeemed the firstborn. God told Israel, “Consecrate to Me all the firstborn, whatever opens the womb among the children of Israel, both of man and beast; it is Mine” (Exodus 12:2). God would claim every firstborn of man and beast among Israel as His personal, consecrated, set apart possession. This consecration, according to verses 11-16, was to be a continual reminder that God had delivered them from Egypt and had done so mightily.
And it shall be, when the LORD brings you into the land of the Canaanites, as He swore to you and your fathers, and gives it to you, that you shall set apart to the LORD all that open the womb, that is, every firstborn that comes from an animal which you have; the males shall be the LORD’S. But every firstborn of a donkey you shall redeem with a lamb; and if you will not redeem it, then you shall break its neck. And all the firstborn of man among your sons you shall redeem. So it shall be, when your son asks you in time to come, saying, ‘What is this?’ that you shall say to him, ‘By strength of hand the LORD brought us out of Egypt, out of the house of bondage. And it came to pass, when Pharaoh was stubborn about letting us go, that the LORD killed all the firstborn in the land of Egypt, both the firstborn of man and the firstborn of beast. Therefore, I sacrifice to the LORD all males that open the womb, but all the firstborn of my sons I redeem.’ It shall be as a sign on your hand and as frontlets between your eyes, for by strength of hand the LORD brought us out of Egypt. (Exodus 13:11-16)
God set apart the Levites to be a replacement for all the firstborn of Israel. They were a purchased people set apart for an exceptional service. They were bought or redeemed with blood (sacrifice). They were unique. They were also a type or a shadow of Christians today. First Peter 2:9-10 reads, “But you are a chosen generation, a royal priesthood, a holy nation, His own special people, that you may proclaim the praises of Him who called you out of darkness into His marvelous light; who once were not a people but are now the people of God, who had not obtained mercy but now have obtained mercy.” God wanted the Levites to live up to, fulfill and appreciate their unique purpose. All Christians should do the same.