Albert Barnes Commentary Numbers 28:11-15

"And in the beginnings of your months ye shall offer a burnt-offering unto Jehovah: two young bullocks, and one ram, seven he-lambs a year old without blemish; and three tenth parts [of an ephah] of fine flour for a meal-offering, mingled with oil, for each bullock; and two tenth parts of fine flour for a meal-offering, mingled with oil, for the one ram; and a tenth part of fine flour mingled with oil for a meal-offering unto every lamb; for a burnt-offering of a sweet savor, an offering made by fire unto Jehovah. And their drink-offerings shall be half a hin of wine for a bullock, and the third part of a hin for the ram, and the fourth part of a hin for a lamb: this is the burnt-offering of every month throughout the months of the year. And one he-goat for a sin-offering unto Jehovah; it shall be offered besides the continual burnt-offering, and the drink-offering thereof." — Numbers 28:11-15 (ASV)

The New-moon offering is also commanded here for the first time. The goat as a sin-offering, though mentioned last, would seem in fact to have been offered first (compare the precedents in Exodus 29; Leviticus 5; Leviticus 8; Leviticus 9; Leviticus 14; Leviticus 16). The sin-offering, which had been contemplated in Numbers 15:22-26 for cases where a sin had been committed ignorantly without the knowledge of the congregation, was from then on not to be offered merely at discretion, as circumstances might seem to require, but to be regularly repeated, at least once a month.