Jamieson, Fausset & Brown

Now to him that is of power--more simply, as in Jde 1:24, "to Him that is able." to stablish--confirm, or uphold you, according to my gospel, and the preaching of Jesus Christ--that is, in conformity with the truths of that Gospel which I preach, and not I only, but all to whom has been committed "the preaching of Jesus Christ." according to the revelation of the mystery--(See on Rom 11:25). which was kept secret since the world began--literally, "which hath been kept in silence during eternal ages."