Charles Ellicott Commentary 2 Corinthians 1:20

"For how many soever be the promises of God, in him is the yea: wherefore also through him is the Amen, unto the glory of God through us." — 2 Corinthians 1:20 (ASV)

All the promises of God . . .—Literally, as many as are the promises of God. Many of the better manuscripts give a different reading: “In him is the Yea, therefore also by him is the Amen to God for glory by our means.”

The thought in either case is the same. The promises of God have been fulfilled and ratified in Christ. He was, as it were, a living incarnate “Amen” to those promises.

Compare Saint John’s use of the word Amen as a name of Christ, the “faithful and true witness” (Revelation 3:14). The words “by us” are determined by the context as referring to the preacher rather than to the hearers of the Word.