The exchange of Levites in place of the first-born did, however, present a difficulty. For God had communicated the number of Levites to Moses in the following way: "Their number amounts to as many as the number of My legion." For, when God came down upon Sinai, twenty-two thousand angels surrounded Him, and just as many men did the Levites number. Outside of these there were three hundred first-born among the Levites that could not well be offered in exchange for the first-born among the other tribes, because their standing was the same as theirs.
As the number of first-born among the other tribes exceeded the number of Levites by two hundred seventy-three, this surplus remained without actual atonement. Hence God ordered Moses to take from them five shekels apiece by the poll as redemption money, and give it to the priests. The sum was fixed upon by God, who said: "Ye sold the first-born of Rachel for five shekels, and for this reason shall ye give as redemption money for every first-born among ye five shekels."