God did not abolish the Law or make it no longer effective.  Doing so would simply be saying that God no longer cared about us, that he had given up all hope of making things right. No, He did better than that.  He sent Christ to fulfill all the righteous requirements of the Law, so that we could be made right with God through Him.  And all of this is done by grace, so that all people everywhere can now be fully reconciled with God.

The Law of Moses exists to reveal true righteousness on a human level.  It shows us how to be fair and even-handed with the people all around us.  It shows us how to live decent lives of justice and truth.  And it still does that, even in the age of grace. 

While no one (in any time or age) has ever been saved by keeping the Law (we are all saved by grace through faith, just as Abraham was (see Genesis 15:1-6), the Law of Moses still holds many benefits in teaching us God's ways, just as it did for Israel in the days of the Exodus.  In the laws and commandments, we see how we should treat each other.