Leviticus 27:10
He shall not alter it, nor change it, a good for a bad, or a bad for a good: and if he shall at all change beast for beast, then it and the exchange thereof shall be holy.
Cross-reference
Leviticus 27:15-33 expands on redemption rules for houses, fields, and tithes, all part of the same system of vowed dedications.
Leviticus 27:13 provides the redemption option for a vowed animal, adding a fifth — a specific case related to the prohibition of substitution.
Leviticus 27:33 repeats the same substitution rule for tithes: no exchanging, and if done, both become holy — directly parallel.
Ezekiel 48:14 forbids exchanging holy land, mirroring Leviticus' ban on exchanging vowed animals — both uphold the inviolability of dedicated things.
Proverbs 20:25 warns against rash vows, complementing Leviticus' rule against changing a vow — both stress careful commitment.
Ecclesiastes 5:6 warns not to treat a vow as a mistake, reinforcing Leviticus' prohibition on substituting vowed animals.