What is the significance of the phrase “and they will reign forever and ever”?

The New Jerusalem is dominated by the throne of God and of the Lamb, as source of the river of life-giving water (Revelation 22:1–2) and as grounds for perfect service to him (Revelation 22:3–4); from him and through him and to him are all things (Romans 11:36). Already the angel had made clear to John that God’s servants would worship (obey, adore) him and see him, and now he adds that these same servants would reign eternally. Their eternal reign is no threat or competition to God’s throne but is instead the ultimate fulfilment of already being co-workers alongside God in his world today (1 Corinthians 3:9; 2 Corinthians 6:1; Ephesians 2:6; see also Matthew 19:28; Revelation 5:10). It is as Jesus promised to those who conquer: I will grant him to sit with me on my throne, as I also conquered and sat down with my Father on his throne (Revelation 3:21). So fully does the Lord God and the Lamb unite his servants into his family that we share with him the privilege of being the source and centre of life in the New Jerusalem; Bride and Bridegroom become one flesh in sacred eternal marriage!