Numbers 1:1 - Coke's Commentary on the Holy Bible

And the Lord spake unto Moses— The Israelites had now left Egypt about thirteen months, and had resided near Mount Sinai almost a year, (compare Exodus 19:1 with this verse) receiving all the foregoing laws and injunctions before they left this place. The Almighty orders a general muster to be made, and an exact poll to be taken of all the Israelitish men, from twenty years old and upwards, the Levites excepted; and a careful distinction to be observed in the tribes, families, and households; for these reasons: 1st, That every one might know, and deliver to his posterity, a clear account from what tribe he descended, and to what family he belonged: 2nd, That the Israelites might see how fully he had made good his promise to Abraham, of multiplying his seed: 3rdly, That they might know what strength they had for war, in case of any attack from their enemies: 4thly, That they might better dispose of their camp about the tabernacle, now that it was erected, and march more regularly when they removed from mount Sinai: and, 5thly, That hereby the genealogy of the Messiah, who was to be born of this nation, might be fully ascertained. It appears from Exodus 40:17 that the tabernacle was erected on the first day of the first month of the second year after their coming out of Egypt; and, as this muster was to be taken on the first day of the second month of the same year, it appears, that what is related in the foregoing book, must have passed in the space of that first month.