In the gospel passage Matthew 4: 12-23, we see Jesus showing the fulfilment of a passage from Isaiah in that out of the darkness, we see the light.  This passage comes after Jesus had been tempted in the wilderness and was then accompanied by angels.  In our trials and tribulations, we ought to reflect on what has happened and where the light shines in our lives.  God is watching us and brings the light in when we go through the darkness.  Quite often, we can lose track of that light in our lives as we embark life in the shadow and become oblivious to where we are or what is going on.  

Jesus furthers our understanding of Isaiah’s passage by expressing the need to repent because the kingdom of heaven is near. 
Repenting is more than just saying sorry.  In asking for forgiveness for our sins, we need to have a conversion of heart, where we take a look at what we have done, to know where we have gone wrong, to own up to it and to have a change of heart.  Repenting is not about making ourselves feel better so that we can sin again. 
Repenting is about seeing the light, having contrition and yearning to improve, so that we do not stay in darkness. 
To have a contrite heart is to have remorse, regret and to want to make things right.  This is not the same thing as saying sorry, because it will make life easier.  Parents and teachers, tell children to say ‘sorry’ and children do so, so that they do not get into trouble with their parents and teachers.  We should evolve from this concept and repent because we know we have done something wrong; we have contrition, and we need to take ownership of what we have done, rather than apologising because it will get people off our back.
‘The kingdom of heaven is close at hand’ can mean different things but have the same outcome.  This could refer to our lives being very short, and we do not have a great deal of time to repent, so repent while you still can.  It can also refer to distance insofar as God is not that far away, and He sees all, and the light that shines means He sees through the darkness. 
And as we say in the Lord’s Prayer – “on earth as it is in heaven’, meaning that tweaking ourselves to be heavenly will bring elements of heaven here on earth.  Regardless of how you perceive it, repenting is not something we can afford to do later.
The passage that Jesus quotes is from Isaiah 9:1.  Following this passage brings out the joy of coming into the light.  As we dwell in darkness, the darkness overpowers us, and our burden gets heavier.  Also, following this passage, Isaiah expresses that a son will be given to us, who will be the Prince of Peace.  Jesus is leading the people to a realisation without directly saying it.  Those who would be familiar with Isaish would have picked this up, and it would become apparent later, to others, that the passage refers to Jesus.