Matthew 12:2

‘But the Pharisees, when they saw it, said to him, “Behold, your disciples do what it is not lawful to do on the sabbath.” '

Some of the Pharisees became aware of what His disciples were doing. It may be that they had been walking with the disciples, professing interest in Jesus' message, while carefully watching for any failures in the behaviour of His disciples, or it may be that it had simply been reported to them by people who saw it, bringing them hurriedly to the scene. Either way they pointed out that He and His disciples (as their Master He could be accounted responsible) were doing what was not lawful on the Sabbath Day.

‘What is not lawful to do.' We should note that this is probably not just a comment, but an official warning. Proceedings could not be taken under the Law against ‘the untaught' at the first offence. The culprits had first to be warned so as to ensure that they did know what the Law was. If the warning was then ignored, proceedings could be taken (compare Acts 4:18 with Matthew 5:17). Thus Jesus and His disciples were being warned that if it happened again proceedings would be taken. The opposition was hardening.

It should be noted that this was not a question of whether the Sabbath should be observed. All would have been agreed on that. It was a question of what should be interpreted as work, and who had the authority to determine it. On the whole the Jews delighted in the Sabbath and rejoiced in it. It set them apart as God's people, and as behaving as God had behaved. But Pharisaic interpretation was strict (in the Qumran community they were even stricter). Jesus' argument is that it is a matter of compassion, and the fact that One Was here Who could authoritatively declare what was allowed on the grounds of compassion.