Why does God require perfection to enter heaven?

God's holiness necessitates that only the perfect and pure can dwell with Him eternally in heaven. As revealed in Revelation 21:27, nothing that defiles or causes an abomination can enter heaven, signifying that God's standard is absolute purity. This is why the Gospel is vital; it offers a way for sinful humans to be deemed righteous through faith in Christ, who fulfilled the law perfectly on behalf of the elect. Thus, believers are clothed in Christ's righteousness, enabling them to stand justified before God.