The Sermon on the Mount is one of the most famous teachings Jesus ever did. However, if you examine what we've just read, I'm surprised anyone stayed around the way He really challenged them......and us. What we're going to see is that Jesus was raising the bar for anyone who thought they could just look at the 10 Commandments and be good. He raised the bar for anyone who would be born again with the Holy Spirit. I hope you stay around.
Light was one of the first things we see in the Bible. In fact, apart from heaven and earth, light was the first thing created and was the first thing spoken into existence. Light gives warmth, but the function Jesus talked about here had to do with enabling people to see.
We have natural light (the sun) and artificial light produced through light bulbs, etc. A light bulb by itself, however, is nothing, much like the believer who is not abiding in Christ. John 15:5 However, when the light bulb is inserted into a lamp, and the lamp plugged into a power source, the bulb will produce light. Likewise, we must make sure we're not only plugged into a power source, but that we're situated in such a place that the light can be seen. If I turn on a lamp, but put it in a closet and shut the door, I'm wasting electricity. What am I doing if I take the light God has given me and hide it somewhere.
This is why verse 16 is so important: Let your light so shine before me that they see your good works and glorify your Father in heaven. "Good works" are not the works that makes God love you, but simply those things that were prepared for you when you were saved. Ephesians 2:8-10 Here's the part that raises the bar. Don't do the right thing because it will cause people to accept you; Do the right thing because it'll make God look good to the world. Talk about something that will cause a civil war between flesh and spirit!
Ask many people on the street about getting into heaven and you'll hear many (too many) justify themselves by saying they're good people that haven't killed anyone, haven't cheated on their spouses and so forth. We know that this type of justification through actions is doomed to failure because no one could keep the law except Jesus.
However, Jesus seemed to not make it easy. Going through life and failing to murder isn't enough; Jesus called people to not even being angry without cause. Jesus taught that not cheating on your spouse was a good thing, but He called people to not even allow yourself to lust after another. Finally, loving your neighbors is ordained by God, but Jesus reminds them that they're also to (gasp) love their enemies.