Deuteronomy 12:6

12:6 And there you must take your burnt offerings, your sacrifices, your tithes, the personal offerings you have prepared, your votive offerings, your freewill offerings, and the firstborn of your herds and flocks.

Deuteronomy 12:17

12:17 You will not be allowed to eat in your villages your tithe of grain, new wine, olive oil, the firstborn of your herd and flock, any votive offerings you have vowed, or your freewill and personal offerings.

Deuteronomy 21:15

Laws Concerning Children

21:15 Suppose a man has two wives, one whom he loves more than the other, and they both bear him sons, with the firstborn being the child of the less loved wife.