Exodus 13:11-13

Young's Literal Translation

¹¹ `And it hath been, when Jehovah bringeth thee in unto the land of the Canaanite, as He hath sworn to thee and to thy fathers, and hath given it to thee,

¹² that thou hast caused every one opening a womb to pass over to Jehovah, and every firstling -- the increase of beasts which thou hast: the males [are] Jehovah's.

¹³ `And every firstling of an ass thou dost ransom with a lamb, and if thou dost not ransom [it], then thou hast beheaded it: and every first-born of man among thy sons thou dost ransom.