Luke 5:27

After this he went out and saw a tax collector named Levi, sitting at the tax booth. And he said to him, “Follow me.” And leaving everything, he rose and followed him.
What was Levi like? The record of his conversion is short, but makes sense in context. The obvious question is why did Levi follow Jesus? He had not been inside the house where Jesus was. He remained outside, a miserable Jewish collaborator, the lowest of the low, manning his tax booth. This was not an impulsive man, eager to rub shoulders with everyone else. Levi sat.

Even when he saw the crowds who had come to hear Jesus, he stayed in his booth. Why would this man, simply hearing the words "Follow me", get up, leave everything and follow him? Levi did not leave everything when the crowds came. He just let them get on with it. Levi did not expect to be part of the action. He sat apart. What changed?

Inside the house, Jesus healed a paralysed man. "Rise, pick up your bed and go home," Jesus said - so he did. On his way out, this paralysed man walked past the tax collector. We know this because Jesus also, when he left the building, "went out and saw a tax collector named Levi sitting at the tax booth".

What had Levi seen? There was already a crowd when the paralysed man arrived, stretchered there by his entourage. They could not get in to see Jesus, and the man was there for a while, waiting as they readied whatever tools and ropes they needed to break through the roof and lower their friend into the place where Jesus was. What were these fools doing? A while later he saw the man leaving and carrying his bed, praising God. But even at this point, he sat at his booth.

What would you have done in Levi's place? I would have wanted to know how this had happened. But even if Levi did not ask, he heard this man glorifying God - speaking of Jesus as God's agent. Maybe he did ask, who knows? 

If he had asked, and if anyone had answered him, he would have heard this - that Jesus explicitly healed the man so that people could "know that the Son of Man has authority on earth to forgive sins". But still Levi sat there.

How do we explain Levi's impulsive decision? He got up, left his booth, and followed the man who could give him what he needed. Forgiveness of sins. He was no longer powerless to change. Here it was: the power and the will to forgive. If he had that, he could leave his booth. But when did he get it? The power came when Jesus himself said to him, "Follow me". He went from knowing about Jesus to knowing Jesus. He heard the direct call of God on his life. God creates what he commands.