For all the promises of God in him are yea, and in him Amen, unto the glory of God by us.
Rather, How many soever be the promises of God in Him is the "yea" ('faithfulness to His word;' contrasted with the "yea and nay," 2 Corinthians 1:19; - i:e., man's inconstancy to one's word).
And in him Amen. 'Aleph (') A B C Delta f g, Vulgate, read 'wherefore also through Him is the Amen' - i:e., In Him is faithfulness, ("yea") to His word, 'wherefore through Him' is the immutable verification of it ("Amen"). As "yea" is His word, so "Amen" is His oath, which makes our assurance of the fulfillment doubly sure. Compare "two immutable things" (namely, His word and His oath) in which it was impossible for God to lie (Hebrews 6:18; Revelation 3:14). All the Old Testament and New Testament promises are secure in their fulfillment for us in Christ.
Unto the glory of God by us - Greek, 'for glory unto God by us' (cf. 2 Corinthians 4:15) i:e., by our ministerial labours; by us His promises and His unchangeable faithfulness to them are proclaimed. Billroth not so well explains, He sets the "yea" of verification to all God's promises, wherefore also through Him the "Amen" of our announcement of it is brought about to the glory of God. Where God saith Yea, we can only say Amen (1 Corinthians 14:16).