Numbers 15:3

15:3 and you make an offering by fire to the Lord from the herd or from the flock (whether a burnt offering or a sacrifice for discharging a vow or as a freewill offering or in your solemn feasts) to create a pleasing aroma to the Lord,

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 16:10

16:10 Then you are to celebrate the Festival of Weeks before the Lord your God with the voluntary offering that you will bring, in proportion to how he has blessed you.