The Heidelberg Catechism, written in 1563, originated in one of the few pockets of Calvinistic faith in the Lutheran and Catholic territories of Germany. Conceived originally as a teaching instrument to promote religious unity in the Palatinate, the catechism soon became a guide for preaching as well. It is a remarkably warm-hearted and personalized confession of faith, eminently deserving of its popularity among Reformed churches to the present day.