On the tenth day: When the twelve days of the dedication commenced cannot be easily determined; but the computation of F. Scacchus seems highly probable. He supposes, that the tabernacle being erected the first day of the first month of the second year after the departure from Egypt, seven days were spent in the consecration of it, and the altar, etc.; and that on the eight day, Moses began to consecrate Aaron and his sons, which lasted seven days more. Then, on the fourteenth day of that month, was the feast day of unleavened bread; which God commanded to be observed in the first month (Numbers 9:1), and which lasted till the 22nd. The rest of the month, we may well suppose, was spent in giving, receiving, and delivering the laws contained in the book of Leviticus; after which, on the first day of the second month, Moses began to number the people, according to the command in the beginning of this book; which may be supposed to have lasted three days. On the fourth, the Levites were numbered; on the next day we may suppose they were offered to God, and given to the Priests; and on the sixth, they were expiated and consecrated, as we read in the following chapter. On the seventh day, their several charges were assigned them (Numbers 4:1); after which, he supposes the princes began to offer, on the eight day of the second month, for the dedication of the altar, which lasted till the nineteenth day inclusively; and on the twentieth day of this month, they removed from Sinai to the wilderness of Paran (Numbers 10:11-12).
Ahiezer: Numbers 1:12, Numbers 2:25