What does Revelation 21:26 and Revelation 22:2 mean? What does the references to the nations mean?
"And they shall bring the glory and honor of the nations into it."
"In the midst of the street of it, and on either side of the river, was there the tree of life, which bare twelve manner of fruits, and yielded her fruit every month: and the leaves of the tree were for the healing of the nations."
The word "nations" means all the people of the world who live in various nations. It is the same word that is also translated as "Gentiles" when it is used to contrast between the Jews and everyone of a non-Jewish nationality.
One of the themes of the New Testament is that the gospel and the promise of salvation was given to all people. "Therefore remember that you, once Gentiles in the flesh--who are called Uncircumcision by what is called the Circumcision made in the flesh by hands-- that at that time you were without Christ, being aliens from the commonwealth of Israel and strangers from the covenants of promise, having no hope and without God in the world. But now in Christ Jesus you who once were far off have been brought near by the blood of Christ" (Ephesians 2:11-13). Unlike the Old Testament which was given to the people of just one nation. "Therefore be careful to observe them; for this is your wisdom and your understanding in the sight of the peoples who will hear all these statutes, and say, 'Surely this great nation is a wise and understanding people.' For what great nation is there that has God so near to it, as the LORD our God is to us, for whatever reason we may call upon Him? And what great nation is there that has such statutes and righteous judgments as are in all this law which I set before you this day?" (Deuteronomy 4:6-8). The Jews had come to believe that salvation was only offered to them and that only by become a part of the Jewish nation could a person be saved. That is why you see Jesus' audience getting angry whenever he pointed out that God had dealings with other nations.
God is emphasizing in Revelation that heaven is opened to people of all nationalities and that salvation ("healing") is given to all people, regardless of their origins.