XXXVI. In addition to “making” the Apostles as a reference to the Old Testament appointment of priests, the number – twelve – is of course related to the twelve tribes of Israel. But that number, too, was chosen in accord with Hebrew thought as an expression of fullness, comprehensiveness, universality (twelve is three – like the stability of a stool – times four – like the four directions; seven is also a number of fullness as three plus four). Indicated here is the intention of Jesus to re-constitute a holy people, built on the foundation of the Twelve.
The Twelve have a two-fold role according to Mark’s Gospel – to be with Jesus, and to be sent out to preach (Mk 3-13-19). They must come to know Him as the one sent by the Father, and in fact one God with the Father, so they can be His witnesses to the world. Because of the Holy Spirit, both are true – they are “with Jesus” no matter where their mission takes them. As they preach Christ, they simultaneously show the emptiness of all false gods and the work of deception by Satan, the Father of Lies. The Word made flesh, the Word of Truth through Whom all things were made, counters falsehood, chaos, subjectivism that makes “my truth” something relative and divisive.
In addition, Matthew adds the element of healing to the mission of the Twelve. This is not primarily medical or psychological as an end in itself. Rather, this concrete healing when granted is a sign pointing to the fullness of life that Jesus will gain for us by His Passion and Resurrection.