Exodus 13:11-13

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

12that thou shalt set apart unto the LORD all that openeth the womb, and every firstling which thou hast that cometh of a beast; the males shall be the LORD’S.

13And 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 firstborn of man among thy sons shalt thou redeem.