What was the sermon on the mount and why was is it critical to christians?

New Testament Matthew 5-7, why don't you read it and we can discuss it and what it means to you and others.
http://www.biblegateway.com/passage/...-7&version=NIV

It is not "critical" it is one of the longest teaching of Christ but it is his death and rising from the dead that is critical to all people.