This text may a little bit over my uneducated head. In it Jesus mentions that "The Law" is not going away and that if you aren't more righteous than the Pharisees you aren't getting in to heaven.
17"Do not think that I have come to abolish the Law or the Prophets; I have not come to abolish them but to fulfill them. 18I tell you the truth, until heaven and earth disappear, not the smallest letter, not the least stroke of a pen, will by any means disappear from the Law until everything is accomplished. 19Anyone who breaks one of the least of these commandments and teaches others to do the same will be called least in the kingdom of heaven, but whoever practices and teaches these commands will be called great in the kingdom of heaven. 20For I tell you that unless your righteousness surpasses that of the Pharisees and the teachers of the law, you will certainly not enter the kingdom of heaven.
So "the Law", as I understand it, is essentially the first five books of the Old Testament. If any of you have read those books you might recall some pretty crazy stuff. For instance (and I'm just flipping through the books at random…there is so much crazy stuff in here)
Exodus 22:5 Anyone who curses his father or mother must be put to death
Leviticus 19:19 Do not mate different kinds of animals
Leviticus 19:27 Do not cut the hair at the sides of your head or clip off the edges of your beard
There are rules defining Clean and Unclean Food, Purification after Childbirth, Regulations about mildew including directions on how to cleanse from mildew, and many other interesting Laws.
If "the Law" stands until "heaven and earth disappear", what are we to do?
I'll tell you what I did…I cheated and read on ahead. In the following scriptures (Matthew 5:21-7:12) Jesus lists off a bunch of rules defining Murder, Adultery, Divorce, Oaths, Prayer, Fasting, and other things. Very interesting stuff which we will get to later.
In reading ahead, I found that that Jesus speaks a lot in extremes, overemphasizing a point to drive it home. I'd say Jesus is trying to balance out His message of Grace by making it very clear that there is a still a standard by which we should live. He ends by saying:
So in everything, do to others what you would have them do to you, for this sums up the Law and the Prophets (Matthew 7:21)
After first saying "Unless your righteousness surpasses that of the Pharisee's…you will not enter the kingdom of heaven", He simplifies "the Law" that the Pharisee's followed so strictly, by saying "Do unto others…". It could be that Jesus is saying don't get caught up in the hypocrisy of the Pharisee's, who followed the letter of the Law but missed out on the bigger picture by being consumed with legalism… I'm not sure.
What I take from Matthew 5:17-21 is this: Jesus has come to offer a new way of Salvation apart from following "the Law", BUT He is not dismissing that Law in any way. We are still responsible to follow the essence of it which is "Do unto others as you would have them do unto you".
This makes me wonder why Christians and Churches spend so little time working to help those in need and instead focus mainly on themselves (see my previous rant here).