John 5:17-20
These verses are in introduction to the teaching that follows. Jesus is telling His disciples that He has not come to abolish the law (the Old Testament) but to fulfil it. There are a few points here that are important to note. First, many Christians believe the Old Testament is not important. Verse 17 states this is wrong. There are important messages to gain from study of the Old Testament, in particular, the message of God’s plan of salvation in Jesus is seen woven throughout the books of the Old Testament. The New Testament and Jesus’ words in particular, rely on the knowledge of the Old Testament and its teaching, in order to understand it properly. Also, Jesus is saying that He has come to fulfil the law by giving it its full meaning.
The law the people of Jesus’ time knew was the hypocritical legalism of the Pharisees. According to their teaching, the external keeping of the law was more important than keeping the law inwardly. Jesus is saying that it is the inward keeping of the law that is important. He warns that the disciples must be more righteous than the scribes and Pharisees or will not enter the kingdom of heaven. Just as the religious institutions of Jesus’ day were caught up in legalism and outward appearances. The “laws” of God, even the Ten Commandments, were broad principles that were intended to be defined in individual consultation with God. However the scribes interpreted the law, which the Pharisees were strict in keeping, and created thousands of regulations believers were expected to follow. This was not what God intended, as Jesus demonstrated by His frequent breaches of these rules. Sadly many religious institutions today are as caught up in legalism and outward appearances as the scribes and Pharisees of Jesus’ time.
According to William Barclay, the essence of God’s law was reverence for God and respect for all men. It is true that the Ten Commandments cover those. Also Jesus’ statement in Mark 12:30-31 that the most important commandment was to “love the Lord your God” with all your heart, soul, mind and strength and to “love your neighbour as yourself” concurs with Barclay’s interpretation. Jesus wanted His disciples to love God, not the law. He wanted the motivation of His disciples to be that of love for God which would carry with it a desire to please God by following the law. He also knew that without the law, we could not be aware of our sinfulness and our need for a saviour.
So be careful that your inward faith, your relationship with Jesus is given more attention than the outward appearances. Better to appear to others to not be following Jesus closely than for Jesus to know you are not spending enough time in relationship with Him.

Matthew 5:14-16
Having taught the disciples that they are the salt of the earth, he presents the same message in a different way. This time he calls them lights of the world. In John 1:4-5 we are told that Jesus contained life and that life was the light of men that shone in the darkness. In verse 9 we are told that the true light gives light to everyone. Now in these verses Jesus is telling His disciples that they are light also. His disciples are to carry on His work in the world and need to be the light just as He is. Unlike Jesus we are not light, but when we have Jesus inside us we can then be light.
Some time ago I mentioned the Lotus is a symbol God frequently gives to me as representing me. A friend who lived in Egypt for some time told me that the Lotus is known as the lighthouse of the desert because night travellers use Lotus to find the oases (living water) at night. This happens because the white blossoms of the Lotus reflect the light and shine like lighthouses through the night. This is the sort of light Jesus is calling his disciples.
In John 9:5 Jesus declared that as long as He was in the world, He was the light of the world. Now He is instructing His disciples to be lights of the world. What He is telling us to do is to be like Him. In being lights of the world, we are required to behave like Jesus and be His light to the world. If we remain in Jesus, then we will shine with His presence in our hearts.
Not also that Jesus told us to be the lights of the world. Many choose instead to be the light of their church and ignore the world. This is not acceptable to Jesus. He requires us to be the light of the world. This means we must live our entire lives behaving acceptably and in a way that brings glory to Jesus. We should show good behaviour to all people. Jesus also requires us to be firm and courageous in standing up for what is right. He does not expect us to sit back and allow wrong decisions to be made. We must stand for our moral values out there in the world and be prepared to be the light that guides others.
In the Message, verse 16 talks about the disciple being required to open up to others. So often people damaged by childhood trauma learn to turn inwards and cut themselves off. For the Christian, this prevents him or her from fulfilling Jesus’ requirement as a disciple to be the light of the world. This is a handy ploy of satan’s to prevent Jesus’ instruction being carried out. Yet we are required to be open and by opening up to others, we prompt people to open up with God, this generous Father in heaven.
So being a light means being like Jesus and shining for all the world to see the glory of God in Jesus.