Originally, in the Greek world, a disciple was a man who bound himself to someone else to acquire practical and theoretical knowledge. In the Hebrew world a disciple was a man who bound himself to the Torah with the Jewish rabbi as his teacher of the Torah. This gave rise to a variety of Rabbinic schools and to rival groups of disciples, each centred upon a teacher. Within the New Testament the word 'disciples' is used of (a) the disciples of John the Baptist (Matt 11.2), (b) the disciples of Moses (John 9.28), (c) the disciples of the Pharisees (Mark 2.18) and (d) the disciples of Jesus. With respect to this latter group the word is used to describe both an inner group of disciples, i.e. the Twelve and, in a much looser sense, of a larger group which followed him during part of his earthly ministry.
It is important to establish that there was a radical difference between discipleship as it related to Jesus and discipleship as it operated in either the Greek world or the world of the Rabbis: "there is a marked difference between a life dedicated to study at the feet of a Rabbi, in which the aim was an increasing knowledge of the Law, which would eventually 'qualify' a student himself to become a rabbi, and the life of the Christian disciple (often not markedly studious by nature!) called to personal loyalty to Jesus in His way" (WD Davies). The Sermon on the Mount, Cambridge 1966, p 133. IH Marshall says much the same when he observes that discipleship "involved personal allegiance (to Jesus) expressed in following him and giving him an exclusive loyalty… Such an attitude went well beyond the normal pupil/teacher relationship and gave the word 'disciple' a new sense. "The Illustrated Bible Dictionary vol 1, IVP 1980. The disciple of Jesus not only learns from Jesus he learns about Jesus. Whereas in the world of the Jewish rabbi prospective disciples sought out a teacher, Jesus called his disciples. Becoming a disciple committed a man not only to a learning process but also to a life of unconditional sacrifice (Matt 10.37; Luke 14.26f) for the whole of life (Matt 10.24f; John11.16).Nowhere is this more clear than in Matt 16.24f where Jesus says, "If anyone would come after me, he must deny himself and take up his cross and follow me." It is well to remember that Jesus warned of the need for a man or woman to sit down and count the cost before becoming a disciple.
Too often the word 'disciple' has been defined solely in terms of its Greek or rabbinic background. The result has been an over-simplistic equation, i.e. disciple = learner. This has provided a basis for some to advocate a wholly indiscriminate baptism, both of adults and children, the only requirement being a willingness to learn and not a whole-hearted commitment to Jesus. There is a failure here to recognise that Jesus poured a whole new meaning into discipleship in so far as it related to him –as he did with everything he touched. If indiscriminate baptism is to be a possibility, biblically, we must seek grounds other than the equation, disciple equals learner.
Of course, there are spurious disciples as there is spurious faith (John 2.23-25) but there can be no question as to the kind of disciples Jesus had in mind when he gave the command to "make disciples…baptising them…".