Exodus 13:12

“Sanctify to Me every firstborn, the first offspring of every womb among the sons of Israel, both of man and beast; it belongs to Me.”

“You shall not delay the offering from the fullness of your harvest and the juice of your wine vat. The firstborn of your sons you shall give to Me.

“For every firstborn among the sons of Israel is Mine, among the men and among the animals; on the day that I struck down all the firstborn in the land of Egypt I sanctified them for Myself.

“You shall set apart as holy to Yahweh your God all the firstborn males that are born of your herd and of your flock; you shall not work with the firstborn of your herd nor shear the firstborn of your flock.

“Moreover, you took your sons and daughters, whom you had borne to Me, and sacrificed them to idols to be devoured. Were your harlotries so small a matter?

(as it is written in the Law of the Lord, “Every firstborn male that opens the womb shall be called holy to the Lord”),