Jamieson, Fausset and Brown on Matthew 12:9

9. And when he was departed thence--but "on another sabbath" (Lu 6:6).

he went into their synagogue--"and taught." He had now, no doubt, arrived in Galilee; but this, it would appear, did not occur at Capernaum, for after it was over, He "withdrew Himelf," it is said "to the sea" (Mr 3:7), whereas Capernaum was at the sea.

And, behold, there was a man which had his hand withered--disabled by paralysis (as in 1Ki 13:4). It was his right hand, as Luke (Lu 6:6) graphically notes.

And they asked him, saying, Is it lawful to heal on the sabbath days? that they might accuse him--Mark and Luke (Mr 3:2; Lu 6:7) say they "watched Him whether He would heal on the sabbath day." They were now come to the length of dogging His steps, to collect materials for a charge of impiety against Him. It is probable that it was to their thoughts rather than their words that Jesus addressed Himself in what follows.