Following Christ means taking certain steps. The first step, which responds to the call, separates the followers from their previous existence. A call to discipleship thus immediately creates a new situation. Staying in the old situation and following Christ mutually exclude each other. At first, that was quite visibly the case. The tax collector had to leave his booth and Peter his nets to follow Jesus. According to our understanding, even back then things could have been quite different. Jesus could have given the tax collector new knowledge of God and left him in his old situation. If Jesus had not been God’s Son become human, then that would have been possible. But because Jesus is the Christ, it has to be made clear from the beginning that his word is not a doctrine. Instead, it creates existence anew. The point was to really walk with Jesus. It was made clear to those he called that they only had one possibility of believing in Jesus, that of leaving everything and going with the incarnate Son of God.
The first step puts the follower into the situation of being able to believe. If people do not follow, they remain behind, then they do not learn to believe. Those called must get out of their situations, in which they cannot believe, into a situation in which faith can begin. This step has no intrinsic worth of its own; it is justified only by the community with Jesus Christ that is attained. As long as Levi sits in the tax collector’s booth and Peter at his nets, they would do their work honestly and loyally, they would have old or new knowledge about God. But if they want to learn to believe in God, they have to follow the Son of God incarnate and walk with him.
Dietrich Bonhoeffer, Discipleship, Chapter 2