The Pharisees come to Jesus and ask, “Why is it your disciples are allowed to do that which is impermissible on the Sabbath?” You’d think Jesus would cite a text about the Sabbath and say, “Here’s why: it’s not really breaking the law of God. The law, in Deuteronomy actually gives us permission to glean. You guys are missing the point.” But Christ doesn’t do that. Instead, he goes to this seemingly random, interesting, odd text, about David on the run from Saul eating the bread of the Tabernacle. You have to ask yourself why he chose this particular text as a defense for his actions. In essence, his argument is this: “Long ago, David did this thing, in a particular circumstance. And this circumstance should remind you of what’s going on now.”
Next, Christ says they can do so, because he is the one who can authorize such a thing as Lord of the Sabbath. This pushes the offense over the top, into a whole other category for the Pharisees.
Lastly, Christ goes on to show the true intention of the day. How grateful can we be that Christ gives us not the explanation we would expect, but the revelation we need.