Ephesians 3:5

Which in other ages was not made known unto, the sons of
men
That is, which mystery of Christ, and of the Gospel, was not made known to men in general, nor so clearly as under the Gospel dispensation. Some hints were given of it to Adam, immediately after his fall; and the Gospel was before preached to Abraham, Moses, and David, and others knew something of it; and it was still more fully dispensed in the times of the prophet Isaiah, and other following prophets: but then the knowledge of it was not so extensive, nor so clear as now; it lay hid in types and shadows, in obscure prophecies and short hints. Moreover, this may have respect particularly to the calling of the Gentiles, as appears from the following words; this was, in some measure, made known, as that in Christ all the nations of the earth should be blessed; that when Shiloh came, to him should the gathering of the people be; that the Messiah should be an ensign of the people, and to him should the Gentiles seek; that he should be the covenant of the people, and a leader and a commander of them; and that there should be great flockings to him; but then this was not known to many, and the time, mode, and circumstances of it were but little understood, and comparatively speaking, it was not known: however, it was not so known,

as it is now revealed unto his holy apostles and prophets by the
spirit.
The apostles and prophets were the superior officers in the Gospel dispensation; the former design the twelve apostles of Christ, and the latter such who had the gift of interpreting the prophecies of the Old Testament, and of foretelling things to come, having received gifts from Christ to fit them for such offices, some apostles, some prophets; and to these a revelation was made of the mystery of the Gospel in general, and of the calling of the Gentiles in particular, by the Spirit, who searches the deep things of God, and reveals them, and leads into all truth; and who, by falling upon the Gentiles, as upon Cornelius and his family, and by the success which he gave to the Gospel in the Gentile world, made their calling clear and manifest. The Complutensian edition reads, "by the Holy Spirit"; and so the Arabic and Ethiopic versions.