For the Son of God, Christ Jesus (the Messiah), Who has been preached among you by us, by myself, Silvanus and Timothy, was not Yes and No; but in Him it is [always the divine] Yes.

For as many as are the promises of God, they all find the Yes [answer] in Him [Christ].  For this reason we also utter the Amen (so be it) to God through Him [in His Person and by His agency] to the glory of God.