The trouble here is that the Pharisees were trying to find a way to condemn Jesus. They were trying to catch him in a fault. The easiest way was to watch him on the sabbath and accuse him of breaking that law.

The Jews were commanded to "remember the sabbath day, to keep it holy," (Ex 20:8). This was the fourth commandment. On this day, they were forbidden to do any work (Ex 20:10). Throughout the Old Testament we see how this law was applied.

• In Ex 31:16-17, the sabbath was given as a sign between God and the children of Israel for ever (Neh 9:14).
• In Ex 16:26-27 some of the Jews violated the sabbath by looking for manna on the seventh day.
• In Ex 31:14-15, capital punishment was commanded for those who worked on the sabbath.
• In Ex 35:3, no fire was to be kindled throughout their habitations on the sabbath.
• In Num 15:32-26, a man gathered sticks on the sabbath and was stoned to death.
• In Neh 10:31, the Jews were not to buy and sell on the sabbath (Neh 13:15-21).
• In Jer 17:21-27 the Jews were warned that their gates would be burned if they continued to violate the sabbath. They continued, so the gates were burned by Nebuchadnezzar.
• In Is. 66:23, during the millennial reign of Jesus, from one sabbath to another, all flesh will come to worship before the Lord (Eze 46:1-3).

So, when the Pharisees saw the disciples eat ears of corn in the field (v.1), they accused them of breaking the sabbath (v.2). Jesus responded by giving them two examples from the Old Testament where the sabbath was violated and God permitted it (vs.3-5). The first was when David ate the shewbread which was for the priests only (1 Sam 21:3-6; Lev 24:5-9). And the second was the violation of the priests each sabbath when they offered the lambs for a burnt offering (Num 28:9-10).

Therefore, the Lord pronounced that the disciples were guiltless for several reasons (vs.6-8):

• The sabbath was made for man so that he would be refreshed (Mk 2:27; Ex 23:12). Merely eating field corn didn’t violate their rest.
• Jesus was greater than the temple (v.6) in which the priests sacrificed the lambs — so, if the priests were blameless then his disciples were blameless, too.
• The Pharisees, covering their wicked and hypocritical hearts with sacrifices (Matt 23), were quick to condemn the disciples. But it was the Pharisees, not the disciples, who were guilty (Hos 6:6; Prov 21:27).
• Jesus is the Lord of the sabbath day (v.8; Gen 2:1-3) with the authority to permit what he will on that day.

Then he went into the synagogue and healed a man with a withered hand (vs.9-13). Of course, the Pharisees used this as an opportunity to try to accuse Jesus of violating the sabbath. Evidently, Jesus’ reasoning in the fields convinced the Jews because they were looking for another way to catch him on the sabbath [remember, at his trial, they never did accuse him of breaking the sabbath].

When they asked him if it was lawful to heal on the sabbath, he replied initially by asking them the same question (Mk 3:4). But they refused to answer, which angered him (Mk 3:5). So, he gave them the example of a man pulling a sheep out of a pit on the sabbath. Since they would do that, then certainly it was lawful to heal on the sabbath. So, he healed the man.

As it turns out, Jesus never did break the law, because that would have been a sin and he committed no sin (2 Cor 5:21; Heb 4:15; 1 Pet 2:22). The Pharisees, on the other hand, violated the sabbath and were caught red handed by the Lord right before his crucifixion. He caught them buying and selling contrary to Neh 10:31 and Neh 13:15-21 on the day that he cleansed the temple in Matt 21:12-13 (see http://www.unknownbible.com/crucified.html).