Numbers 18:16

16 When they are a month old, you must redeem them at the redemption price set at five shekelsa of silver, according to the sanctuary shekel, which weighs twenty gerahs.

Read Numbers 18:16 Using Other Translations

And those that are to be redeemed from a month old shalt thou redeem, according to thine estimation, for the money of five shekels, after the shekel of the sanctuary, which is twenty gerahs.
And their redemption price (at a month old you shall redeem them) you shall fix at five shekels in silver, according to the shekel of the sanctuary, which is twenty gerahs.
Redeem them when they are one month old. The redemption price is five pieces of silver (as measured by the weight of the sanctuary shekel, which equals twenty gerahs).

What does Numbers 18:16 mean?

John Gill's Exposition of the Bible
Numbers 18:16

And those that are to be redeemed
Which is to be understood not of unclean beasts last mentioned, for they were redeemed with lambs and not with money; and after they were eight days and not a month old, as follows, ( Exodus 13:13 ) ( 22:30 ) ; but of the firstborn of men:

from a month old shalt thou redeem, according to thine estimation:
that is, take the redemption money next mentioned; and though both time and price are fixed, yet said to be according to the estimation of the priest; see ( Leviticus 27:5 Leviticus 27:6 ) ;

for the money of five shekels;
which was about eleven or twelve shillings of our money, and is the price given for the redemption of the firstborn, when the Levites were taken in their stead, ( Numbers 3:47 ) ;

after the shekel of the sanctuary, which [is] twenty gerahs,
(See Gill on Numbers 3:47); of the manner of redeeming the firstborn, (See Gill on Exodus 13:15).

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