John Gill Bible Commentary

And if it be from five years old, even unto to twenty years old,.... Not that one of five years old is supposed to vow or to make an estimation, but one grown up, that says, the estimation of this little one, who is five years of age, be upon me; and such an one was bound to pay the value of him, which is as follows: then thy estimation shall be of the male twenty shekels, and for the female ten shekels; which were for the one above two pounds, and for the other more than one pound; these were valued at a less price than the former, partly because, generally speaking, there are more die between the age of five and the age of twenty years than between twenty and sixty; and partly because within that time they are not capable of so much work and service as in the latter; and it may be observed, that the females of this age are not valued in proportion to the females of the other; the estimation of these being just half that of the males, whereas that of the other is more than half; the reason is, that women above twenty years of age, their service bears, a better proportion to that of men, than that of young women to young men under twenty.