Deuteronomy 15:18-20 New International Version - UK (NIVUK)
18 Do not consider it a hardship to set your servant free, because their service to you these six years has been worth twice as much as that of a hired hand. And the Lord your God will bless you in everything you do.
The firstborn animals
19 Set apart for the Lord your God every firstborn male of your herds and flocks. Do not put the firstborn of your oxen to work, and do not shear the firstborn of your sheep. 20 Each year you and your family are to eat them in the presence of the Lord your God at the place he will choose.