Exodus 13:12-15

12that thou shalt offer unto Jehovah all that breaketh open the womb, and every firstling that cometh of cattle which is thine: the males [shall be] Jehovah's.

13And every firstling of an ass shalt thou ransom with a lamb; and if thou do not ransom it, thou shalt break its neck; and every firstborn of a man among thy sons shalt thou ransom.

14And it shall be when thy son asketh thee in time to come, saying, What is this? that thou shalt say to him, With a powerful hand Jehovah brought us out from Egypt, out of the house of bondage.

15And it came to pass, when Pharaoh stubbornly refused to let us go, that Jehovah slew all the firstborn in the land of Egypt, both the firstborn of men and the firstborn of cattle: therefore I sacrifice to Jehovah all that breaketh open the womb — being males; and every firstborn of my children I ransom.