As the Gospels relate, Jesus himself called persons to be his disciples, which meant, first of all, wandering around with Jesus, and in word and deed bringing the kingdom of God closer to other people. Discipleship was based on a call. It involved personal allegiance to him, expressed in following him and giving him an exclusive loyalty (Lk 14:26-33). At least in some cases it meant abandonment of home, business ties and possessions, but in every case a readiness to accept the claims of Jesus first, whatever the cost, was demanded. Such an attitude went well beyond the normal pupil-teacher relationship and gave the word ‘disciple’ a new sense. Faith in Jesus and allegiance to him are what determine the fate of men at the last judgement (Lk 12-8f).
One becomes a disciple only when called by Jesus himself. The initiative always lies with Jesus alone; apart from his call, there is no recognizable motive for one to become a disciple and follow him. There are instances in Gospels when the would-be disciple takes the initiative, but all of these attempts fail, and there is no evidence that discipleship would have resulted. There is the example of the rich young man who turns to Jesus, but when the call to discipleship confronts him, he goes away sadly. According to Luke 9:57-60 several came to Jesus with the intention to be his disciples, yet failed to become disciples because they remained bound to their past.
The call of Jesus demanded a total break with the past. The disciples immediately left their families and their vocations and followed Jesus. So it could become a direct condition of