John Calvin Commentary Numbers 8:16

"For they are wholly given unto me from among the children of Israel; instead of all that openeth the womb, even the first-born of all the children of Israel, have I taken them unto me." — Numbers 8:16 (ASV)

For they are wholly given. Lest the other tribes should complain that the number of the people was diminished, God declares that the Levites were set apart from the lineage of Abraham, since He had acquired them for Himself when He struck all the first-born of Egypt. For it is certain that the first-born of the people, as well as those of their animals, were miraculously rescued from the common destruction. Therefore, since God delivered them by special privilege, He thus bound them to Himself by the blessing of their redemption.

But this reason would seem no longer to apply when God, in demanding the price of redemption, set the first-born free,¹⁷⁸ as was stated elsewhere; otherwise, He would require the same thing twice, which would be unjust. The solution to this, however, is straightforward: when, in the first census, the first-born of the twelve tribes were counted, they were found to exceed the Levites in number. An exchange was then made, namely, that all the first-born of the twelve tribes, numbering 22,000, should be free from this obligation, and that God should take the Levites in their place as His ministers. Only 273 were redeemed, because this was the number by which they exceeded the Levites. In this way, it came about that God was satisfied with these just and equal terms, so as not to oppress the people with a heavy burden.

However, this compensation, made only on that one particular day, did not prevent the Israelites from owing their children yet to be born to God. Therefore, since this obligation still remained with them regarding their descendants, the law was passed that they should redeem their first-born. If anyone should object that it was not fair for those born of the Levites to be consecrated to God—I reply that on this point there was no unfairness: for from whatever tribe they might be descended, they were already His property, together with all their offspring; the condition of the people was not therefore made worse by the exchange; and so, in all fairness, God appointed for the future at what price the Israelites should redeem their first-born.

In saying that they were “given” to Him, He means to assert that they were His by compact;¹⁷⁹ and in this sense, He declares that from the day He struck the first-born of Egypt, the first-born of Israel had become His. He then adds that He took the Levites at that time, as if to say that He dealt with His people only concerning past events.

¹⁷⁸ Vide Numbers 3:43–51..

¹⁷⁹ “En disant qu’ils luy ont este donnez, il n’entend pas que ce soit de don gratuit, mais qu’ils luy appartienent comme de paction faite;” in saying ;” in saying that they were given to Him, He does not mean as a gratuitous gift, but that they belonged to Him as by agreement made. — Him, He does not mean as a gratuitous gift, but that they belonged to Him as by agreement made. — Fr..