What does the Bible say about heaven and holiness?

Isaiah 35:8-9 illustrates that heaven, being an abode of holiness, is a place where the unclean cannot enter. It emphasizes that only the redeemed—those who have been made holy through Christ—will walk there. Heaven is designed for a renewed people who possess a nature harmonious with its purity. The word of God teaches that true fitness for heaven comes from sharing in the divine nature and being transformed by the Holy Spirit, which aligns one's desires and affections with the holiness of heaven, making it a fitting home for the believer.