This article consists of notes on Lord's Day 31 of the Heidelberg Catechism.

Preaching is the proclamation of the gospel and the promise of forgiveness. In this context, the minister can preach God's judgment. Preaching judgment is also crucial for promoting holiness and the hate of sin. This is discussed in light of Lord's Day 31 of the Heidelberg Catechism.

In this article on Lord's Day 31 of the Heidelberg Catechism, the author shows how the kingdom of heaven is opened by the keys the Lord Jesus himself gave to the disciples. Preaching is the central key is also discussed. The central text is Matthew 16:19.