Matthew had doubtless for years been relating the teaching of Jesus as he remembered and indeed probably had recorded it- he was a tax collector, and was accustomed to take careful daily notes and to write down his records. Is it not obviously for this function that he is appointed, so abruptly and so early in the Narrative of Mark, at the first threat of peril? What is he to do? Why, of course, what he had always done- record everything. The ancient tax collector was the inveterate note-taker of antiquity. He left nothing to memory, but wrote everything down. The papyri have illustrated this abundantly, as the pages upon pages of their Greek remains show. And this is why Matthew virtually disappears from the narrative after his call; he was the secretary, taking his notes. He performs no striking act, asks no questions, plays no leading part; that was not his role. He merely records. To the ancient reader who knew tax collectors and what their chief activities were, this hardly needed saying. It was self-evident. And this is why the call of Matthew which appears to us so abruptly and detached, seemed to them self-explanatory. Jesus' teaching from now on had a recorder, as Isaiah had had, long ago, and that was what had saved Isaiah and his message from oblivion. Can anyone suppose Jesus and his circle, with their great regard for Isaiah, failed to see this?
from pages 116-117, Matthew, Apostle and Evangelist