Mark 3:4

Mark 3:4; Matthew 12:10 shows that the question of our Lord was preceded by one from the Pharisees, just as His command had been occasioned by ‘their thoughts' or ‘reasonings' (Luke 6:8).

Is it lawful? i.e., according to the Mosaic law.

To do good, or to do harm. To benefit, or to injure, rather than to do right or to do wrong. This is repeated yet more forcibly: to save a life or to kill? Our Lord thus establishes the propriety of works of mercy on the Sabbath, even according to the Mosaic law (see on Matthew 12:11-12, where the falling of a sheep into a pit is introduced). His opponents were silenced; and his authority as ‘Lord also of the Sabbath' (chap. Mark 2:28) is then vindicated by the miracle.