"Hear me, all of you, and understand. Nothing that enters one from outside can defile that person; but the things that come out from within are what defile."
Scriptures (Old Testament) spoke about purity laws. The were also talking about food laws. These laws were like signposts. They were pointing out to something. But once you reach the destination the you do not need the signposts anymore.
Jesus argument is that these purity laws and other food laws do not actually touch the real human problem. It is the kingdom of God that touches the real human problem. So Jesus brings to completion the covenant that God made.
Jesus, here, is making a distinction between laws and principles of life. Laws are time bound and they are for a particular situation. But the principles are true in every situation at every place at anytime and for everyone. The principles are: respect for person, love of the other, respect for life, freedom, goodness etc. These are in a sense eternal and they are true.
But the laws are true in one country and they are not practiced in another.
So Jesus is telling his listeners to understand this basic difference. Man is more important than the laws. Respect for life is more important than the sabbath laws etc.
Listen to the kingdom of God. Understand the kingdom of God.
