John Calvin Commentary Numbers 28:9

"And on the sabbath day two he-lambs a year old without blemish, and two tenth parts [of an ephah] of fine flour for a meal-offering, mingled with oil, and the drink-offering thereof:" — Numbers 28:9 (ASV)

And on the Sabbath-day. What was omitted in the former passage is supplied here: that is, on the Sabbath the continual sacrifice was to be doubled, and two lambs offered instead of one. This was reasonable because, as the seventh day was especially dedicated to God, it should be exalted above other days by some extraordinary and distinctive mark.

He also commands greater sacrifices to be offered at the beginning of the month or new moon, namely, two bullocks, one ram, and a goat for a sin-offering. For we know that the first day of every month was consecrated to God, so that the people might more frequently have the remembrance of their religious duties renewed. Furthermore, the goat for an atonement for sin was added, so that every month they should present themselves as guilty before God to avert His wrath.