Now we get to the heart of what was wrong with the Pharisees’ way of thinking. They had read the Prophets and the Histories and saw that God had brought judgement on their people because they did not follow God’s commands (which is true). So they decided that in order to get God’s blessing they needed to follow the Law perfectly. But there are over 600 commands in the Torah, and some of them are fairly obscure and subtle. They memorized them anyway. And for some, they put up fences around what God had said: the Sabbath is a day of rest and you are not to do any work (Ex. 20:8–11). But what is “work”? How are you going to obey the command if you don’t know? The extra rules that the Pharisees created were intended to help people obey the Law, but in reality just made life harder. (E.g.: Cover your mirrors on the Sabbath, because if your wife looks and sees a gray hair she might pull it out, which would be work.)
Back to our passage. Jesus and His disciples were going through a field, and somebody got peckish and started eating the grain. This is allowed in the Law of Moses (Deut. 23:25). However the way this works is to take the ear off the stalk, then rub it between your hands so that the seeds separate from the chaff so that you can blow it away. According to the Pharisees, you can pick up food to eat it, but that is like threshing, which is clearly work.
Some Pharisees see what Jesus’s disciples have done. (How, I wonder? Why were they out in the fields on the Sabbath?) When they confront Jesus about it, He reminds them of the time David and his men ate the bread that had been dedicated to God. According to the Law, only priests and their families should have been allowed to eat this bread (Lev 24:5–9) but the priest there gave it to David for he and his men were on the run from King Saul and had no provisions (1 Sam 21:3–6).
Jesus then says something extraordinary. “The Son of Man is lord of the Sabbath.” (v. 5) “Son of Man” is how Jesus most often refers to Himself, and it is how Daniel describes the Messiah when He is given dominion and authority over the nations in Daniel 7. The Sabbath was created by God when He rested on the seventh day of Creation, but Jesus is claiming authority over it. Effectively, He says it’s not up to the Pharisees to decide what’s lawful to do on the Sabbath, but Him.
Let us read Your Word with clarity, so that we may do precisely what is says, and not cling to our traditions which were created by fallible men.