Jesus says to a man ‘Follow me,’ and immediately the man gets up and leaves everything and follows him. This man is Levi, who is today identified with St Matthew. Before having been called by Christ, St Matthew was a tax collector. In the time of Jesus tax collectors had a bad reputation. They were considered to be collaborators with the Roman authorities. They abused the people, extracting much from them in order to make themselves rich, as well as giving a portion to the emperor.
So the tax collector of the Gospel is a rich man, and he makes much money because he acts fraudulently towards the people. Since this sort of person has a direct relation with the general public they are sometimes referred to as ‘publicans.’ And it is from this group, out of this world considered to be sinful and profane, that Jesus calls one of his disciples. (Mk 2:13-17)
He is the one who will baptize with the Holy Spirit. Now I have seen and testified that he is the Son of God."