William Burkitt on Matthew 12:7

Learn hence, That the law of mercy is much more excellent than the law of ceremonies; and where both cannot be observed, the less must give place to the greater. God never intended that the ceremonies of his service in the first table, should hinder works of mercy prescribed in the second table. All God's commands are for man's good. Where both cannot be obeyed, he will have the moral duty performed, and the ceremonial service omitted: he will have mercy and not sacrifice: that is, he will have mercy rather than sacrifice, where both cannot be had.