In Old Testament times, the gates of Jerusalem were closed at night to prevent a surprise night-time attack (Nehemiah 7:3), and at any time during the day when the city was threatened. The gates were also locked and barred on the Sabbath, preventing trading on God's holy day (Nehemiah 13:19). But the New Jerusalem will be different. The gates will always be open (Isaiah 60:11) because there is no night, no enemies and no trading: no special day to be holy because all days are holy. The Lord will be the light, diffusing His glory equally among His people.

Instead of trade, the nations will bring their tribute (the praise payment) to the city. The church is already practising that sacrifice of praise (Hebrews 13:15), which will be the theme-song of heaven (Revelation 4:11; 5:12; 7:12). Everybody in the city will have been made pure and clean by the blood of the Lamb (Revelation 7:14).

There is no impurity in God's presence, and so nobody whose lifestyle is untouched by the cleansing blood will be allowed to enter. Of course we have all sinned, but those who repent and welcome the Lord to refine them have their names in His book of life – they have accepted that Jesus has died as punishment for their sins. Eternity will not just be like this beautiful world but with nicer people and will last longer. Eternity will be radically different: there will be no more sea (21:1), no more tears, death, sorrow, crying or pain (21:4), no more sinners (21:8), no more sun or moon (21:23), no more night (21:25), no more sin or evil (21:27), no more disease or injuries (22:2) and no more curse (22:3).

A natural question is, 'How can I be certain I will be there?' The answer cannot include doing more good works because they can never cancel out our sin. There is only one way to be certain, "Believe in the Lord Jesus Christ and you will be saved" (Acts 16:31). To believe is not a mental assent to facts but a wholehearted commitment to trust and obey. We come to Christ believing the promises in His Word that whoever comes to Him, He will never turn away (John 6:35-37). We come admitting our sin and seeking mercy (1 John 1:9); we come trusting that His blood makes us clean from every sin (1 John 1:7). Are you trusting like that? Then you may be confident of heaven.