Heidelberg Catechism, Lord's Day 31
Lord's Day 31 of the Heidelberg Catechism addresses the believer's sanctification and grateful obedience as the proper response to God's justifying grace in Christ. This catechetical exposition provides foundational instruction on how the justified are called to live holy lives in service to God, making it essential material for understanding Reformed teaching on the Christian life and catechetical instruction.
[Lord's Day 31 text - parse manually from https://www.crcna.org/welcome/beliefs/confessions/heidelberg-catechism]