Numbers 3:13

13. All the firstborn are mine This is a claim founded on the sovereignty of Jehovah, as is seen by the declaration, I am the Lord. As he had chosen Israel to be his firstborn (Exodus 4:22, note) by a sovereign national election to certain earthly privileges not to life everlasting so he exercised the prerogative of selecting a certain class in Israel to be devoted to his especial service. The intimation in this verse is, that the firstborn were saved from the destroyer because they were set apart or hallowed into Jehovah, and not that they were hallowed because they were spared. Hallowed Hebrew, kadash; Greek, αγιαζω ; Vulgate, sanctifico. The two senses of these words are: 1.) To set apart from secular to holy uses. 2.) To cleanse, to purify: of things, a physical cleansing; of persons, a spiritual as well as a physical purification is signified. When the Levites took the place of the firstborn they were not only set apart, but they were washed also. See Numbers 8:6-7. Hence the figures of the physical and spiritual cleansing from all filthiness of the flesh and spirit enjoined by St. Paul in 2 Corinthians 7:1, and by James in Numbers 4:8. “Hallowed,” in this verse, signifies set apart. The firstborn were never ceremonially washed and initiated into the service of the tabernacle, because of the almost immediate substitution of the Levites.