Leviticus 27:8

27:8 If he is too poor to pay the conversion value, he must stand the person before the priest and the priest will establish his conversion value; according to what the man who made the vow can afford, the priest will establish his conversion value.

Leviticus 27:26

Redemption of the Firstborn

27:26 “‘Surely no man may consecrate a firstborn that already belongs to the Lord as a firstborn among the animals; whether it is an ox or a sheep, it belongs to the Lord.