This devotional explores Question 83 of the Heidelberg Catechism, identifying the preaching of the gospel and church discipline as the two keys that open and close the kingdom of heaven. The sermon explains that while the gospel invites all to believe, true faith is evidenced by a desire to amend one's life and obey Christ, as supported by passages in John and 1 Corinthians. It highlights the necessity of church discipline to exclude unrepentant sinners, not as an end in itself, but as a warning that aims to lead them back to repentance. The tone is instructional and sobering, emphasizing the seriousness of the church's duty to maintain purity while extending grace to those who return to the Father.