Isaiah 65:16 - Matthew Poole's English Annotations on the Holy Bible

I will bring it to pass, that over all the world, if any man bless himself, or bless another, it shall be in God Amen. So the Hebrew (we translate it the God of truth). Amen is a name given to Christ, Revelation 3:14, These things saith the Amen, the faithful and true witness; being here applied to God, many think it makes a great proof of the Godhead of Christ, and judge the sense of this text to be, that under the times of the gospel men should not bless themselves (as before) in the names of Abraham, and Isaac, and Jacob, but in the name of Christ, in the God Amen; nor is this an improbable sense. Others taking it more appellatively, by Elohim Amen, here understand that God who shows himself true and faithful in his promises. In like manner it is prophesied, that those that swear (by which some understand worship God, others, calling God to be a witness) should swear by the God of truth, or in the God of truth; either worshipping God in Christ the Amen, or calling the faithful God to attest their sincerity, or swearing by that God who hath approved his truth and faithfulness by saving and delivering his people. Because the former troubles are forgotten, and because they are hid from mine eyes; because they shall see what God promised is fulfilled, the troubles of his people are at an end, and they are hid from God's eyes, that is, they are at an end.