Leviticus 27:6

From a month old even unto five years old. — That is, if a parent, or any other person, devotes his or anyone else’s child to the sanctuary, he is obliged to be redeemed according to the prescribed valuation. The formula used in such a case during the second Temple was, “Behold the estimation of this my boy, or this my girl, or of that boy or that girl, be upon me.”

The male five shekels of silver. — As at this tender age the service of a child is not of much value, the vower is to pay for a boy 12s. 11d.

The female... three shekels of silver. — The girl being proportionately less valuable, is to be redeemed at 7s. 9d.