Albert Barnes on Matthew 12:12

A man better than a sheep. Of more consequence, or value. If you would show an act of kindness to a brute beast on the Sabbath, how much more important is it to evince similar kindness to one made in the image of God! one for whom the Saviour came to die, and who may be raised up to everlasting life.

It is lawful to do well. This was universally allowed by the Jews in the abstract; and Jesus only showed them that the principle on which they acted in other things applied with more force to the case before him, and that the act which he was about to perform was, by their own confession, lawful.