New Defender's Study Bible Notes
21:12 twelve gates. The description of the glorious holy city, the new Jerusalem, is too detailed to admit of anything but literal interpretation, though there have been many efforts to try to spiritualize it. There is every reason to believe that John is describing exactly what he saw, and that God means exactly what He says (note the warning in Revelation 22:18-19). In other words, the holy city is a literal city on a literal earth, with dimensions and descriptions exactly as recorded.
21:12 twelve tribes. The fact that both the twelve tribes of Israel and the twelve apostles of the Lamb (Revelation 21:14) are inscribed on the city’s foundational structures indicates that “the bride, the Lamb’s wife” (Revelation 21:9) who will indwell and personify the city, is composed of believers from both old and new covenants, both before and after the first coming of Christ, Israel and the church. Compare also Ephesians 2:14, 19-21.