“For all the firstborn among the children of Israel are mine, both man and animal. On the day that I struck all the firstborn in the land of Egypt, I sanctified them for myself.”
Numbers 8:17 (WEB)
Context Reading
15“After that, the Levites shall go in to do the service of the Tent of Meeting. You shall cleanse them, and offer them as a wave offering. 16For they are wholly given to me from among the children of Israel; instead of all who open the womb, even the firstborn of all the children of Israel, I have taken them to me. 17For all the firstborn among the children of Israel are mine, both man and animal. On the day that I struck all the firstborn in the land of Egypt, I sanctified them for myself. 18I have taken the Levites instead of all the firstborn among the children of Israel. 19I have given the Levites as a gift to Aaron and to his sons from among the children of Israel, to do the service of the children of Israel in the Tent of Meeting, and to make atonement for the children of Israel, so that there will be no plague among the children of Israel when the children of Israel come near to the sanctuary.”