“If the vow is an animal that may be offered as an offering to the LORD, all of it that he gives to the LORD is holy.
This is part of the law concerning singular vows, extraordinary ones, which though God did not expressly insist on, yet, if they were consistent with and conformable to the general precepts, he would be well pleased with. Note, We should not only ask, What must we do, but, What may we do, for the glory and honour of God?
Commenting on Leviticus 27:1-13
He shall not alter it nor change it,.... Some think these two words signify the same, but Abarbinel (s) makes them different; according to him, to "alter" is for one of another kind, as one of the herd for one of the flock, or the contrary; and to "change" for one of the same kind: a good for a bad, or a bad for a...
if it be a beast, whereof men bring an offering unto the Lord--a clean beast. After it had been vowed, it could neither be employed in common purposes nor exchanged for an equivalent--it must be sacrificed--or if, through some discovered blemish, it was unsuitable for the altar, it might be sold, and the money applied for the sacred service.