Our Gospel today concludes Chapter Five of Matthew's Gospel, a passage that echoes Chapter Twenty of Exodus.
In Chapter Twenty of Exodus Moses summoned the heads of the Israelites up to the height of Mt. Sinai, going on then to issue the Ten Commandments of the Old Law. In Chapter Five of Matthew's Gospel Jesus called the Apostles to his side high on a hill. Then he issued the Beatitudes that embodied the spirit of the New Law.
The Pharisees were saying that Jesus was abolishing the Law and the Prophets by his eating with non-Jews, and by his disregarding the prohibitions they had added to the Law of Moses. But Jesus, in Chapter Five of Matthew's Gospel insisted that far from abolishing the Law, he was actually fulfilling it. The Law said "You shall not kill," but fulfilling that, Jesus said we should not be angry with brothers. The Law said "You shall not commit adultery," but Jesus completed the Law by saying "You shall not lust."
In the end, our English translators quoted Jesus as saying we should be perfect as our heavenly Father is" But, since being as perfect as God is an unreasonable aim, Our English texts would do better to translate Matthew's word directly as "You must strive to be well rounded."