It was fitting that Christ should not commit his doctrine to writing.

First, on account of his dignity; for the more excellent the teacher, the more excellent should be his manner of teaching. Consequently it was fitting that Christ, as the most excellent of teachers, should adopt that manner of teaching whereby his doctrine is imprinted on the hearts of his hearers. . . . For writings are ordained, as to an end, unto the imprinting of doctrine on the hearts of the hearers.

Secondly, on account of the excellence of Christ’s doctrine, which cannot be expressed in writing [quae litteris comprehendi non potest]. ... If Christ had committed his doctrine to writing men would have had no deeper thought of his doctrine than that which appears on the surface of the writing.

Thirdly, that his doctrine might reach all in an orderly manner; Himself teaching his disciples immediately, and they subsequently teaching others by preaching and writing ; whereas if He himself had written, his doctrine would have reached all immediately.

(Ad. 3m-). Those who were unwilling to believe what the apostles wrote of Christ would have refused to believe the writings of Christ, whom they deemed to work miracles by the magic art