Teacher, which is the greatest commandment in the law?  Jesus replied, Love the Lord your God with all your heart and with all your soul and with all your mind.  This is the first and greatest commandment.  And the second is like it: Love your neighbor as yourself.  All the Law and the Prophets hang on these two commandments.                      Matthew 22:36-40

As Jesus went on from there, He saw a man named Matthew sitting at the tax collector's booth.  Follow Me, He told him, and Matthew got up and followed Him.                                         Matthew 9:9

The Lord gave two statements in the two verses mentioned above.  The first in response to a question.  The second as a command to a tax collector.  The first was stated to a respectable member of the Jewish community, in fact one of the most respected, a Pharisee.  The second was stated to a hated member of Jewish society, in fact there wasn't much worse than being a tax collector, it was considered worse than being a gentile pagan.  Though said in different contexts, these two statements reflect much of the heart of the ministry of Jesus. 

Jesus was creating a new community.  But in many ways it was not new at all.  The command to love one's enemy had its root in the Law (Exodus 23:4-5) and is suggested in the text that says to love your neighbor (Leviticus 19:18).  The concern for those outside of the Jewish community didn't originate in the ministry of Jesus either, it goes back to Exodus as well (Exodus 22:21 and 23:9).  Jesus said that he did come to abolish the Law, but to fulfill the Law (Matthew 5:17).  He rebuked the Jewish leaders who had kept the smaller matters of the Law, but had neglected the more important matters of the Law (Matthew 23:23).  He told them in the same sermon that they were behaving just like their forefathers who had killed the prophets (Matthew 23:29-32).   The prophets of the Old Testament had come rebuking the Israelites of their day for neglecting their covenant with the LORD, and now God's own Son had come doing the same thing to the Israelite leadership of His day.  Just as they had treated the prophets, they would also treat the Son (Matthew 21:33-46).  As He stated, the Kingdom would be taken from them and given to a people who would produce fruit.  That new people is called the church, new but in some ways not new.  Membership in that new community is extended to all who will do just as Matthew did, follow Him.