Charles Hodge on Ephesians 3:8

V. 8. To me, adds the apostle, who am less than the least of all saints, is this grace given, that I should preach among the Gentiles, the unsearchable riches of Christ.

By the word saints is to be understood not the apostles, but the people of God, who are "called to be saints," 1 Cor. 1, 7. Rom. 1, 7. Less than the least, ἐλαχιστοτέρος, a comparative formed from a superlative. It was not merely the sense of his sinfulness in general, which weighed so heavily on the apostle’s conscience. It was the sin of persecuting Christ, which he could never forgive himself. As soon as God revealed his Son in him, and he apprehended the infinite excellence and love of Christ, the sin of rejecting and blaspheming such a Saviour appeared so great that all other sins seemed as comparatively nothing. Paul’s experience in this matter is the type of the experience of other Christians. It is the sin of unbelief; the sin of rejecting Christ, of which, agreeably to our Saviour’s own declaration, the Holy Spirit is sent to convince the world. John 16, 9.

To one thus guilty it was a great favour to be allowed to preach Christ. The expression τὸν ἀνεξιχνίαστον πλοῦτος τοῦ Χριστοῦ, unsearchable riches of Christ; riches which cannot be traced; past finding out, may mean either the riches or blessings which Christ bestows, or the riches which he possesses. Both ideas may be included, though the latter is doubtless the more prominent. The unsearchable riches of Christ, are the fulness of the Godhead, the plenitude of all divine glories and perfections which dwell in him; the fulness of grace to pardon, to sanctify and save; every thing in short, which renders him the satisfying portion of the soul.