Adam Clarke on Matthew 12:12

How much then is a man better than a sheep? - Our Lord's argument is what is called argumentum ad hominem; they are taken on their own ground, and confuted on their own maxims and conduct. There are many persons who call themselves Christians, who do more for a beast of burden or pleasure than they do for a man for whom Christ died! Many spend that on coursers, spaniels, and hounds, of which multitudes of the followers of Christ are destitute: - but this also shall come to judgment.

Wherefore, it is lawful to do well, etc. - This was allowed by a multitude of Jewish canons. See Schoettgen.