Numbers 29:39

29:39 “‘These things you must present to the Lord at your appointed times, in addition to your vows and your freewill offerings, as your burnt offerings, your grain offerings, your drink offerings, and your peace offerings.’”

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,