“If it was Paul who revealed that Christ gave Himself a ransom ‘for all’ (1 Tim. 2:6) as opposed to the “many” in Israel (Matt. 20:28), how do we explain John 1:29?”
“…John seeth Jesus…and saith, Behold the Lamb of God, which taketh away the sin of the world.”
John was a prophet (Luke 7:28), and the prophets didn’t always understand their own prophecies (1 Pet. 1:11), especially when it came to “the sufferings of Christ.” God knew that this would probably trouble the prophets, so He comforted them by explaining that “not unto themselves, but unto us they did minister the things” that they prophesied (1 Pet. 1:12).
We know that no one who heard John make his statement understood that Christ would die for the sins of the world, for some of the 12 heard it, but didn’t understand it (Luke 18:31-34). Not even Satan understood it (1 Cor. 2:7,8), or else he wouldn’t have instigated Judas to betray the Lord (Luke 22:3,4).
So the ransom Christ made for all men might have been prophesied in John 1:29, but it wasn’t “testified” until the “due time” came for Paul to be “ordained a preacher and an apostle” (1 Tim. 2:6,7). source