Leviticus 27:6

And if it be from a month old even unto five years old, then thy estimation shall be of the male five shekels of silver, and for the female thy estimation shall be three shekels of silver.

Cross-references

Numbers 18:14-16 confirms the five-shekel redemption price for a firstborn male from a month old, identical to the valuation here.

Numbers 3:47 uses the same five-shekel valuation per head for redeeming the surplus firstborn, directly applying this price.

Numbers 3:40-43 also counts children from a month old, using the same age threshold for the firstborn redemption census.