Deuteronomy 15:19

Every first-born that shall be born among thy kine and thy sheep, thou shalt sanctify the males to the Lord thy God; thou shalt not work with thy first-born calf, and thou shalt not shear the first-born of thy sheep.

All the firstling males that come of thy herd and of thy flock thou shalt sanctify unto the Lord thy God: thou shalt do no work with the firstling of thy bullock, nor shear the firstling of thy sheep.

You shall dedicate all the firstborn males that are born of your herd and of your flock to Yahweh your God. You shall do no work with the firstborn of your herd, nor shear the firstborn of your flock.