John Gills Exposition of the Bible Commentary - Numbers 18:17
But the firstling of a cow, or the firstling of a sheep, or the firstling of a goat, thou shalt not redeem ,.... That is, shalt not take the redemption price for them, but the creatures themselves; which they, the priests, were to take for their own use: they are holy ; separated to the Lord, and therefore not to be used in common by men, but were sacred to the Lord, or became the property of his priests; see Deuteronomy 15:19 ; how they were to be made use of follows: thou shalt... read more
John Gills Exposition of the Bible Commentary - 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 ; 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 ... read more