שאו את ראש בני ישראל , “take a census of the sum of Children of Israel;” according to Rav b’chor shor, this census was performed by means of each person included handing over a shekel, as opposed to the census in Exodus 30,13, where only the total number of Israelite males between the ages of 20 and 60 was of interest. Here we find that the number counted in each tribe is listed separately, and they were listed according to families, i.e. each individual was of consequence. In Numbers, in the fortieth year after the Exodus it was of interest to number of members of each tribe all of whom had replaced the generation that had been condemned to die in the desert. This latter count did not include a single person who had been counted by Moses and Aaron at this time.

ויהיו בני ראובן בכור ישראל, “the number of males counted of the tribe of Reuven, Yaakov’s firstborn son was etc.” this is pointed out, as when it came to the marching in order of the tribes, Yehudah was the first. Reuven was mentioned here first is that he was Yaakov’s firstborn son.

במספר שמות לגגלתם, “according to the number of their names, head by head.” Why does the word לגלגלתם occur only in connection with the members of the tribe of Reuven and Shimon, and none of the other tribes? The reason is that when Yaakov spoke to each of his sons prior to dying, he chided both Reuven and Shimon, instead of giving them an outright blessing. They were therefore in need of atonement, forgiveness. The function of counting by means of the silver coins was in order to achieve atonement, [although these descendants had no special need to atone for the sins of their forefathers. Ed.] At any rate, Moses wished to assure them that they had no longer any need for atonement.

והלוים למטה אבותם לא התפקדו בתוכם, and the Levites according to their tribal affiliations had not been included in this census. The reason was that the basis of counting them was not the same; they were counted from thirty days and up instead from twenty years and up. They were also only counted from thirty years and up when they were ready to perform their duties. (Numbers 4,3). (Compare Bamidbar Rabbah 1,12)

אך את מטה לוי לא תפקוד, “but do not count the tribe of Levi;” this verse excludes the tribe of Levi from the decree of requiring atonement for the sin of dying in the desert which was a decree that was going to be imposed on the males who had been adults at the time of the Exodus after the spies came back declaring that the people could not conquer the Land of Canaan. (Numbers 14,29) Seeing that would be so, G–d did not even want to count them here with the other tribes of Israel.