That by revelation. Some might imagine, that, in attempting to discharge the office of an apostle, he had acted rashly, and was now paying the penalty of his rashness. It was this that made him so earnest in pleading the Divine authority for all his transactions. The present instance, on account of its novelty, had few supporters; and therefore he calls it a mystery. By this name he endeavors to remove the prejudice which the general displeasure at the event was fitted to excite. His own personal interest in the matter was less regarded than that of the Ephesians, who were deeply concerned in the information, that, through the settled purpose of God, they had been called by Paul's ministry. Lest what is little known should forthwith become the object of suspicion, the word mystery places it in opposition to the perverse judgments and opinions which were then prevalent in the world. By revelation he made known to me the mystery. Paul draws the line of distinction between himself and those fanatics, who ascribe to God and to the Holy Spirit their own idle dreams. The false apostles boast of revelations, but it is a false boast. Paul was persuaded that his revelation was true, could prove it to others, and speaks of it as a fact of which no doubt could be entertained. As I wrote a little before. This refers either to a rapid glance at the same subject in the second chapter, or -- which appears to be the general opinion -- to another Epistle. If the former exposition be adopted, it will be proper to translate, as I wrote before in few words; for the subject had received nothing more than a passing notice; but the latter being, as I have said, the prevailing opinion, I prefer translating, as I wrote a little before. The phrase, (en oligo,) which Erasmus has translated in a few words, appears rather to refer to time. On this supposition there would be an implied comparison between the present and the former writings. But nothing would be more unlike the fact, than to contrast them on the score of brevity; for a more concise mode of expression than this passing glance can hardly be imagined. The phrase, a little before, seems purposely to be used as an appeal to their remembrance of a recent occurrence, though I do not insist on this point. There is more difficulty in the next verse.

How that by revelation - see the notes at Galatians 1:12. He refers to the revelation which was made to him when he was called to the apostolic office, that the gospel was to be preached to the Gentiles, and that he was converted for the special purpose of carrying it to them; see Acts 9:15; Acts 22:21.
Unto me the mystery - The hitherto concealed truth that the gospel was to be preached to the Gentiles; see the notes, Ephesians 1:9, on the meaning of the word "mystery."
As I wrote afore in few words - Margin, "a little before." To what this refers commentators are not agreed. Bloomfield, Doddridge, Rosenmuller, Erasmus, Grotius, Locke, and others, suppose that he refers to what he had written in the two previous chapters respecting the plan of God to call the Gentiles to his kingdom. Calvin supposes that he refers to some former epistle which he had written to them, but which is now lost. Hc remarks in regard to this, "If the solicitude of Paul be rightly considered; if his vigilance and assiduity; if his zeal and studious habits; if his kindness and promptitude in assisting his brethren, it is easy to suppose that he wrote many epistles publicly and privately to this place and to that place. But those only which the Lord saw necessary to the welfare of his church has he taken care to have preserved." In this opinion there is nothing in itself improbable (compare introduction to Isaiah, section 5 (1)), but it may be doubted whether Paul here refers to any such epistle. The addition which he makes, "whereby, when ye read," etc., seems rather to imply that he refers to what he had just written.

By revelation he made known unto me - Instead of εγνωρισε, he made known, εγνωρισθη, was made known, is the reading of ABCD*FG, several others, both the Syriac, Coptic, Slavonic, Vulgate, and Itala, with Clemens, Cyril, Chrysostom, Theodoret, Damascenus, and others: it is doubtless the true reading.
The apostle wishes the Ephesians to understand that it was not an opinion of his own, or a doctrine which he was taught by others, or which he had gathered from the ancient prophets; but one that came to him by immediate revelation from God, as he had informed them before in a few words, referring to what he had said Ephesians 1:9-12.

How that by revelation he made known unto me the mystery,.... Or "is made known unto me": so the Alexandrian copy, and some others, and the Vulgate Latin version. The Gospel, which is sometimes called a mystery, the mystery of the Gospel, the mystery of godliness, and the mystery of faith: the several doctrines of the Gospel are the mysteries of the kingdom of heaven; such as a trinity of persons in the Godhead, the union of the two natures in Christ, the saints' union to Christ, and communion with him, the resurrection of the dead, and the change of living saints, and the whole doctrine of salvation by Christ, of justification by his righteousness, pardon by his blood, and atonement by his sacrifice; and this was made known to the apostle, not in a mere notional and speculative way, but in a spiritual and saving manner; not by men, for he was not taught by men, nor did he receive it from them, but had it by the revelation of Jesus Christ, and by the spirit of wisdom and revelation in the knowledge of him:
as I wrote afore in few words: in the two first chapters of this epistle, which are a compendium of the mystery of the Gospel, in its several parts; as predestination, election, redemption, regeneration, and salvation by free grace.

he made known--The oldest manuscripts read, "That by revelation was the mystery (namely, of the admission of the Gentiles, Ephesians 3:6; Ephesians 1:9) made known unto me (Galatians 1:12)."
as I wrote afore--namely, in this Epistle (Ephesians 1:9-10), the words of which he partly repeats.

The mystery - Of salvation by Christ alone, and that both to Jews and gentiles. As I wrote before - Namely, Ephesians 1:9-10; the very words of which passage he here repeats.