Luke 6: On a Sabbath, while he was going through the grainfields, his disciples plucked and ate some heads of grain, rubbing them in their hands.  But some of the Pharisees said, “Why are you doing what is not lawful to do on the Sabbath?”  And Jesus answered them, “Have you not read what David did when he was hungry, he and those who were with him:  how he entered the house of God and took and ate the bread of the Presence, which is not lawful for any but the priests to eat, and also gave it to those with him?”  And he said to them, “The Son of Man is lord of the Sabbath.”
As Jesus travelled around Galilee, Pharisees, who usually hung around Jerusalem, followed Him, listening to His teachings, watching Him and assessing Him and His work. They are waiting for Him to trip up. Their attitude will prove to be more of jealousy and a desire to keep control than a defence of the truth. It is hard not to imagine Jesus seeing these inspectors and doing things for the purpose of correcting them in public. Jesus has the disciples walk through a field of grain and pick it, rub their hands together in order to separate the wheat from the chaff and then eat the kernels of grain. He knows these Pharisees well enough to know that this will provoke a challenge.
The Law prohibited work on the Sabbath. The Jewish leaders over the centuries had added commentaries to the law so that people could really know how to keep it. “Work” was given a very broad definition and what Jesus and His disciples did here was considered threshing grain.
When the Pharisees ask why Jesus and His followers are breaking the Sabbath, they are not being entirely correct. What they are breaking is not the Sabbath, but the common understanding of what the Sabbath regulations meant. And what happened is what often happens – the tradition became more important than the law itself. Jesus has not broken the Law. He has broken the tradition that had developed.
What the Pharisees did with the Law, especially the Sabbath Law, is what people still do with the rules that God gives the church. The Bible says not to get drunk and people turn it in a commandment not to drink at all. The Bible says not to forsake the assembling of ourselves with the people of God and people turn it into guilt trips about being at some church function five or six nights a week. The Bible says to flee from ungodliness and we turn it into a matter of never associating with anyone who does not believe as we do. Over time, our rules become more important than the ones laid down by God.
At some point there will be a reaction against this kind of legalism and the result will be a style of Christianity that has no rules at all – not even God’s. People are pendulum swingers and we travel from one extreme to the other. Excessive rules give way to no rules at all. Grace becomes a licence for immorality and licentious living. Nothing is seen to be wrong.
The worst case scenario is two kinds of Christianity – one that says that we are saved because we keep the rules – which is nothing other than an abandonment of the Gospel because of self righteousness; and one that says we are saved by grace and there are no rules. This is immorality dressed up in religious garments. Neither of these two extremes have anything to do with the Gospel. They are both wrong and they both condemn people to hell. They both need to be abandoned.
The solution to these twin evils is the biblical Gospel. We are saved by the free unmerited grace of God in Christ and empowered by that Gospel to live a holy life. Probably the best summary of it is Ephesians 2:8-10.
 For by grace you have been saved through faith. And this is not your own doing; it is the gift of God,  not a result of works, so that no one may boast.  For we are his workmanship, created in Christ Jesus for good works, which God prepared beforehand, that we should walk in them.
The very fact that most believers know Ephesians 2:8-9 and not verse 10 is an indication of the problem. We are saved by the grace of God through faith in Jesus Christ, which is a gift in itself. This grace will always, always, always, produce holy living which is where verse 10 takes us – “created in Christ Jesus to do good works which He had prepared beforehand that we should walk in them”.
Do not trust your works – that is a denial of grace. Do not think that there are no works to do – that is a denial of grace. We must not be Pharisees and invent our own rules and call them the Word of God. And we must not abandon all rules in the name of correcting the Pharisees.