For the Son of God, Christ Jesus, who was preached among you by us—by me and Silvanus and Timothy—was not yes and no, but is yes in Him. For as many as are the promises of God, in Him they are yes; therefore also through Him is our Amen to the glory of God through us. (1:19–20)
Throughout the history of the church, heretics have always assaulted the nature of Christ, and the false apostles at Corinth appear to be no exception in their effort to diminish Him. Having slanderously accused Paul of being untrustworthy because of his change in travel plans, they also alleged that his teaching on the Lord Jesus was untrustworthy. Responding to their attack on his Lord, Paul emphasized Christ’s nature as the God-man by using the full, rich title the Son of God, Christ Jesus.
Paul was not the only one who preached the truths of the Son of God to the Corinthians; Silvanus and Timothy had preached the message to them. Silvanus (Silas) was a prominent leader in the Jerusalem church. The Jerusalem Council entrusted him to carry its decision to the church at Antioch (Acts 15:22). He later became Paul’s companion on the apostle’s second missionary journey, replacing Barnabas (Acts 15:39–40). Timothy was Paul’s beloved son in the faith. As the son of a Jewish Christian mother and a pagan Gentile father (Acts 16:1), he was uniquely qualified to minister alongside the apostle. Both Silvanus and Timothy had ministered with Paul at Corinth (Acts 18:5). Their preaching was not untrustworthy, it was not yes and no, but was a firm, unwavering, resounding yes to God’s truth in Jesus Christ.
Then Paul sums up the glory of Christ by reminding the Corinthians that as many as are the promises of God, in Him they are yes. All of God’s salvation promises—of blessing, peace, joy, goodness, fellowship, forgiveness, strength, and hope of eternal life—are yes, meaning they all come true, in Christ. They are all made possible by His person and work. After His resurrection, Jesus told His disciples, “All things which are written about Me in the Law of Moses and the Prophets and the Psalms must be fulfilled” (Luke 24:44). In 1 Corinthians 1:30 Paul declared that “Christ Jesus … became to us wisdom from God, and righteousness and sanctification, and redemption.” To the Colossians he wrote, “For it was the Father’s good pleasure for all the fullness to dwell in Him.… For in Him all the fullness of Deity dwells in bodily form” (Col. 1:19; 2:9). It was the realization of “the surpassing value of knowing Christ Jesus [as his] Lord” that made Paul willing to suffer “the loss of all things, and count them but rubbish so that [he might] gain Christ” (Phil. 3:8).
Then Paul drove home the point of his argument by reminding the Corinthians, Therefore also through Him is our Amen to the glory of God through us. Amen is a solemn affirmation of the truthfulness of a statement (cf. Rom. 1:25; 9:5; 11:36; 15:33; 16:27; Gal. 1:5; Eph. 3:21; Phil. 4:20; 1 Tim. 1:17; 6:16; 2 Tim. 4:18; Heb. 13:21; 1 Peter 4:11; 5:11; 2 Peter 3:18; Jude 25; Rev. 1:6; 7:12). When Paul, Silas, and Timothy preached the gospel, it was all about Christ, who by His glorious work brings to pass all salvation realities. The Corinthians probably even had joined in saying Amen to the glory of God. The congregation had affirmed that the preachers reliably spoke God’s truth about Christ when they believed the gospel message Paul and his companions preached, and it transformed their lives. How utterly absurd, Paul argued, to accept and experience the gospel message as reliable, but consider those who preached it unreliable. How ridiculous to trust Paul’s word about eternal things, but not about mundane things like travel plans.
The apostle who was exacting in communicating the true gospel of Christ was also exacting in the lesser matters of life. God did not choose an unstable, unreliable apostle to preach His truth.
1:20 / In verse 20a Paul explains (For, gar) why his message of Jesus Christ as Son of God was unequivocally confirmed to the Corinthians. Just as in verse 18 the faithfulness of God substantiates the veracity of Paul’s general apostolic “word” (including statements about his travel plans), so also here divine promises substantiate Paul’s more specific apostolic message of the gospel.
As Paul has mentioned repeatedly and in various ways in the previous context, the Corinthians are sons of God and thus brothers with Paul (cf. vv. 1, 2, 3). Hence, when Paul refers here to the “promises” that have already been confirmed to the Corinthians, he may have in view particularly the divine adoption of sons (cf. 2 Cor. 6:18, quoting 2 Sam. 7:14) that the Corinthians enjoy in Christ, the messianic Son of God promised beforehand through the ot prophets (Rom. 1:2–4). The only other use of the term in the letter comes at 2 Corinthians 7:1 and refers to an ot messianic adoption text (2 Sam. 7:14) as among the promises that Paul and the Corinthians already have. This does not, of course, exclude other promises from resonating with the text, especially since divine adoptive sonship includes Abrahamic heirship (cf. Gal. 3:26, 29; 4:1–7; Rom. 8:15, 17). Paul’s message of Jesus Christ as Son of God was unequivocally confirmed to the Corinthians, for the latter participate in the sonship of the Son of God, in whom the promises are affirmed by their fulfillment (“Yes”).
In verse 20b Paul draws an inference (And so, dio kai) from the fact that in Christ the Corinthians participate in the promises through Paul’s preaching. Whatever this line may mean in particular, it seems clear that Paul portrays himself as a revelatory mediator. Amen is a transliteration of a Hebrew word that serves to confirm what has been said before. The Corinthians were familiar with this use of Amen (cf. 1 Cor. 14:16). Here, the Amen is spoken by Christ (through him) in that the promises spoken beforehand are fulfilled in him. That affirmation is, in turn, communicated by Paul (by us) to others, including the Corinthians. All of this has a doxological purpose (to the glory of God).
 MacArthur, J. F., Jr. (2003). 2 Corinthians (pp. 43–44). Chicago: Moody Publishers.
 Scott, J. M. (2011). 2 Corinthians (pp. 40–41). Grand Rapids, MI: Baker Books.