Ephesians 3:8

They who go to the physician's have not merely to go there and nothing further; they have to learn how to treat themselves, and to apply remedies. And so with us then who come here, we must not do this and nothing else, we must learn our lesson, the surpassing lowliness of Paul. What? when he was about to speak of the vastness of the grace of God, hear what he saith, "Unto me, who am less than the least of all saints, was this grace given." Lowliness indeed it was even to bewail his former sins, although blotted out, and to make mention of them, and to hold himself within his true measure as where he calls himself "a blasphemer, and a persecutor, and injurious;" yet nothing was equal to this: for "formerly," saith he, such was I; and again he calls himself, "one born out of due time." But that after so many great and good deeds and at that time he should thus humble himself, and call himself "less than the least of all," this is indeed great and surpassing moderation. "To one who am less than the least of all saints;" he saith not, "than the Apostles." So that that expression is less strong than this before us. There his words are, "I am not meet to be called an Apostle." Here he says that he is even "less than the least of all saints;" "to me," saith he, "who am less than the least of all saints was this grace given." Paul himself was sent to the Gentiles, the other Apostles to the Circumsion. So that the more marvellous and astonishing commission was given, saith he, "to me, who am less than the least." And this too was of grace, that he that was least should have the greatest things entrusted to him; that he should be made the herald of these tidings. For he that is made a herald of the greater tidings, is in this way great.

"To preach unto the Gentiles the unsearchable riches of Christ." If His "riches are unsearchable," and that too after his appearing, much more is His essence. If it is still a mystery, much more was it before it was made known; for a mystery he calls it on this account, because neither did the Angels know it, nor was it manifest to any one else.