“And when Jesus finished these sayings, the crowds were astonished at his teaching, for he was teaching them as one who had authority, and not as their scribes.” (Matthew 7:28-29).
In the Sermon on the Mount, Jesus does something only God could do. He speaks as one who has authority over the Law of God. He is not an interpreter of the law (a scribe or Pharisee) but a definer and giver of the law.
Throughout the sermon Jesus says this phrase, “You have heard that it was said…(then quotes an OT law), but I say to you… (then adds to the OT law).” Did you catch that? Jesus brought up an OT law, a law given to Moses from the very mouth of God on Mount Sini, and then Jesus adds to the law by the phrase “but I say to you…”
If you read between the lines it is clear what Jesus is doing. He is claiming to have the same authority on this mount, as Yahweh did on the other mount generations before. To any scribe or Pharisee listening to this message, their hands are filling with rocks because this man is speaking as God.
And that is exactly what Jesus is doing. He is speaking with the same authority as God, because He is God. That’s why the Sermon on the Mount is not just a good sermon, it’s a God sermon. And the message is clear, God is not simply concerned about His people acting right, He is concerned about them being right. And that doesn’t come through keeping all the rules giving on the first mount, it comes by receiving a new heart from the man standing on the second mount.