Charles Ellicott Commentary Numbers 15:4

"then shall he that offereth his oblation offer unto Jehovah a meal-offering of a tenth part [of an ephah] of fine flour mingled with the fourth part of a hin of oil:" — Numbers 15:4 (ASV)

A meat offering of a tenth deal of flour ... — The meal offering and the drink offering which are ordered here to be brought when a lamb was offered in performance of a vow, or as a freewill offering, or at the solemn feasts, are the same as those which were appointed to be offered with the morning and evening lamb (Exodus 29:38–40). Meal offerings and drink offerings had already been prescribed in connection with the three great feasts (Leviticus 23:13; Leviticus 23:18; Leviticus 23:37).