Numbers 8:17 in the King James Version
For all the firstborn of the children of Israel are mine, both man and beast: on the day that I smote every firstborn in the land of Egypt I sanctified them for myself.
Context
16 For 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.
17 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.
18 I have taken the Levites instead of all the firstborn among the children of Israel.