Exodus 13:11-13

11. And it shall be, when Jehovah shall bring thee into the land of the Canaanite, as he sware unto thee and to thy fathers, and shall give it thee,

that  thou shalt set apart unto Jehovah all that openeth the womb, and every firstling which thou hast that cometh of a beast; the males shall be Jehovah's.
And every firstling of an ass thou shalt redeem with a lamb; and if thou wilt not redeem it, then thou shalt break its neck: and  all the first-born of man among thy sons shalt thou redeem.