Deuteronomy 15:19 in the King James Version
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.
Context
18 It shall not seem hard to you when you let him go free from you, for he has been double the value of a hired hand as he served you six years. The LORD your God will bless you in all that you do.
19 You shall dedicate all the firstborn males that are born of your herd and of your flock to the LORD your God. You shall do no work with the firstborn of your herd, nor shear the firstborn of your flock.
20 You shall eat it before the LORD your God year by year in the place which the LORD shall choose, you and your household.