Revelation 21:2: “I saw the holy city, New Jerusalem, coming down out of heaven from God, prepared as a bride adorned for her husband.”
New Jerusalem is holy because God is holy (Lev. 11:44 quoted in 1 Peter 1:16) and the city is saturated with God’s holiness. This God, who is Triune, operates on us and in us to make us holy to match New Jerusalem.
1 Corinthians 1:2 – those “who have been sanctified* in Christ Jesus”
Romans 15:16 – “sanctified in the Holy Spirit”
These verses speak of our sanctification, our being made holy, in position. This occurs, and is complete, when we first believe in the Lord. This is Acts 26:18 – “those who have been sanctified by faith in Me.” And Hebrews 10:10 – “we have been sanctified through the offering of the body of Jesus Christ once for all.”
To match New Jerusalem’s purity and transparency, it is not enough to be holy in position. After our initial, positional sanctification we also need to be saturated with God’s holiness.
Hebrews 10:14 refers to the process of being saturated: “those who are being sanctified.” Ephesians 5:26 tells us how this is accomplished: “He [Christ] might sanctify her [the church, including every believer], cleansing her by the washing of the water in the word.”
The goal of this washing is that Christ, at His second coming, “might present the church to Himself glorious…holy and without blemish” (5:27). This holy and glorious condition, without any spot or wrinkle or blemish matches the holy city, New Jerusalem.
* The English words holy/holiness and sanctify/sanctification are translations of closely related New Testament Greek words. They seem very different because holy came into English from an Anglo-Saxon root and sanctification came from a Latin root.