The document contrasts Mount Sinai, which represents the Old Testament law, with Mount Zion, which represents God's grace.
Mount Sinai instilled fear through displays of God's power, while Mount Zion invites believers into God's presence. The law could not be obeyed, but through Jesus, God offers forgiveness and a new covenant.
The passage warns that those who refuse God will face consequences, just as the Israelites did. But for believers, Jesus endured God's judgment, so they can receive grace rather than punishment. Believers are called to live gratefully under God's kingdom, which will never be shaken.