Significantly, it was to Paul, not Peter, that βthe secret of the gospelβ was first revealed. (See Eph. 3:1-3;Β 6:19). It was he who was first sent forth to proclaim the doctrine of salvation, and to reveal all that had been accomplished at Calvary.
The Old Testament Scriptures had predicted that the sins of others would be laid upon Christ, but they had not explained how Christβs death would be the basis for the sinnerβs justification.
Many a criminal has gone free because his crimes have been βpinned onβ another, but this has by no means justified the criminal! Some sincere Christians seem to think that substitution is the very acme of Bible truth, when in fact it is but the beginning, for substitution in itself does not imply the sinnerβs justification.
It is also true that salvation had been offered before Paul. Men were told what to do to be saved β though the terms varied from time to time β and were even instructed, upon Christβs arrival, to believe in Him for salvation. At that time sacrifices, circumcision, water baptism, etc., were still required for the remission of sins β and any believer would approach God in His way. This is why these religious rites were observed throughout our Lordβs earthly ministry and even through Pentecost.
The Apostle Paul, however, was later raised up to make known βthe secret of the gospel,β and to proclaim the glorious accomplishments of Christ at Calvary. All the rich blessings so thrillingly set forth in Paulβs epistles flow to us from Calvary. Ours is a heavenly position because He came to earth to die for our sins. Ours is βthe hope of glory,β because He suffered our shame. Ours is the blessing of βpeace with Godβ because He bore Godβs wrath upon sin. Ours is relief from the load of sin because He bore that load. Every one of our βall spiritual blessingsβ (Eph. 1:3) comes to us from Calvary. Paulβs βsecret of the gospelβ centers in Calvary. Little wonder St. Paul calls his preaching βthe preaching of the crossβΒ (1 Cor. 1:18). source
[β¦] The Spirit did not, of course, reveal all truth at one time. βThe Law was given by Moses;β later the prophesies were penned by men of God as they were βmoved by the Holy Spiritβ and still later our Lord uttered truth βkept secret since the world began.β [β¦]
[β¦] beginning with the ministry of the Apostle Paul, an infinitely moreΒ pleasingΒ secret was [β¦]