A number of times in his letters, Paul mentions “the mystery.” Concerning it, he says “in other generations [it] was not made known to the sons of men, as it has now been revealed to [God’s] holy apostles and prophets in the Spirit” (Eph. 3:5). So, what was that “mystery”?
Tragically, some are teaching that it was previously hidden truth that superseded, and even nullified, the teaching of Jesus. They claim, for example, that God revealed to Paul that salvation is granted through God’s grace under the new covenant, whereas under the old covenant, it was allegedly earned through works. And since Jesus’ earthly ministry was conducted under the old covenant, they say that explains why He so often tied obedience to salvation in His teaching and preaching. Now that the new covenant has been inaugurated, and the “mystery” has been revealed, we realize that we can ignore everything Jesus said that ties salvation to holiness, as it has no application to new covenant believers who are saved by grace!