Comentario citado sobre Números 3:46

AND IT SHALL BE WHEN THE ETERNAL SHALL BRING THEE INTO THE LAND OF THE CANAANITES. This is stated because the law of that which “openeth the womb” [mentioned in Verse 12], applied only from the time they came to the Land of Israel.³⁹¹See my Hebrew commentary p. 344 for correctness of this reading as based on Ramban manuscript. It is also borne out by Ramban’s statement further on in this section: “But the commandment… did not apply to the firstborn in the wilderness.”
In line with the plain meaning of Scripture, the verse, Sanctify unto Me all the firstborn, [mentioned in Verse 2 above] means all the firstborn living at that time. Since He redeemed them from death when He smote in the land of Egypt, He commanded [in that verse above] that they be sanctified to Him to do the work of G-d, whatever He will command them to do. He did not command them at this time concerning the redemption of the firstborn, but only after He exchanged them for the Levites and He commanded the redemption of the firstborn that were over and above the number of the Levites.³⁹²Numbers 3:44-47. But the commandment [as expressed in the verse, Sanctify unto Me all the firstborn], did not apply to the firstborn in the wilderness. Now, [in the verse before us], He commanded that when they shall come into the Land of Israel, the law should apply to the firstborn of both man and beast³⁹³Verse 12. and the firstling of an ass,³⁹⁴Verse 13. and then He commanded the law of their redemption for the generations.³⁹⁴Verse 13.

TAKE THE LEVITES INSTEAD OF ALL THE FIRSTBORN AMONG THE CHILDREN OF ISRAEL. The firstborns had become sanctified to G-d from the time that He commanded Sanctify unto Me all the firstborn … among the children of Israel etc.¹⁸¹Exodus 13:2. There were thus many firstborns in Israel who had not been redeemed until now, since it had not yet been said who would “redeem” them, for it was only now that the priests became sanctified, and [Israel] had not yet been commanded about the gifts of the priesthood.¹⁸²Further, 18:8-20. Thus they [the firstborns] continued without restriction in their sanctity, and it is possible that they performed the Service of the offerings, as our Rabbis have said.¹⁸³Zebachim 115 b.
The correct opinion appears to me to be that not all these firstborns were born in the desert in one year, for the people did not increase there so rapidly [that there should have been twenty-two thousand firstborns in one year, corresponding to the twenty-two thousand Levites, with an excess over the Levites of two hundred and seventy-three].¹⁸⁴Verse 46. Rather, all firstborns of Israel [alive at that time, even those born many years previously] were counted, for they were all sanctified, as I have explained there.¹⁸⁵Exodus 13:11. See my Hebrew commentary here p. 204. Now, He exchanged them for the Levites, and this was their “redemption,” and He commanded to redeem those that exceeded [the number of the Levites by means of each one giving five shekels]. And He gave the redemption-money to Aaron and his sons, as is the commandment for all generations [that a firstborn son be redeemed by giving five shekels to a priest].

ולקחת חמשת חמשת שקלים, "You shall take 5 shekels apiece, etc." Why did the Torah commence this verse with the conjunctive letter ו before the word לקחת seeing it is part and parcel of the legislation commencing in verse 46 about the redemption of the extra 273 firstborn for whom no equivalent Levites could be found? Perhaps the letter ו alludes to the fact that the money redeeming these 273 people was to come out of the pockets of the firstborn and not out of the pockets of the Levites. You could have reasoned that the process of redemption would be parallel to the redemption of the animals of the Levites when the money for the redemption had to be paid by the Levites. It would have been logical to conclude that the Levites had to pay. To disabuse us of such thinking the Torah had to write מבכור בני ישראל, "from the firstborn of the Israelites" (at the end of verse 46). The Torah spells this out when it came to the actual carrying out of these instructions in verse 50. The Torah describes Moses as taking the redemption money from the firstborn, not from the Levites. In our verse the additional information is the amount of the redemption money per person, i.e. 5 shekels each. The letter ו means that we are dealing with a second commandment. The Torah repeats the word תקח to tell us there is a third commandment i.e. that the five shekels are "holy shekels" worth 20 geyrah each. Every detail mentioned here was an essential part of the procedure.