John Gill Commentary Deuteronomy 23:22

"But if thou shalt forbear to vow, it shall be no sin in thee." — Deuteronomy 23:22 (ASV)

But if you shall forbear to vow
That a man might do, though there was ability; it was expected indeed that men should vow and bring freewill offerings in proportion to their ability; whether they were of the greater sort, of the herd and flock, or of fowls, or even of fine flour, these were acceptable to the Lord: but if they were not vowed and brought,

it shall be no sin in you ;
no charge of guilt be brought or punishment laid; it should not be reckoned a crime, nor be punishable in any respect, and especially where there was a willing mind and no ability; otherwise negligence, niggardliness, and ingratitude, are not well pleasing in the sight of God.