Adam Clarke on Ephesians 3:5

Which in other ages was not made known - That the calling of the Gentiles was made known by the prophets in different ages of the Jewish Church is exceedingly clear; but it certainly was not made known in that clear and precise manner in which it was now revealed by the Spirit unto the ministers of the New Testament: nor was it made known unto them at all, that the Gentiles should find salvation without coming under the yoke of the Mosaic law, and that the Jews themselves should be freed from that yoke of bondage; these were discoveries totally new, and now revealed for the first time by the Spirit of God.