The Heidelberg Catechism (1563) was composed in the city of Heidelberg, Germany, at the request of Elector Frederick III, who ruled the province of the Palatinate from 1559 to 1576. The new catechism was intended as a tool for teaching young people, a guide for preaching in the provincial churches, and a form of confessional unity among the several Protestant factions in the Palatinate. An old tradition credits Zacharias Ursinus and Caspar Olevianus with being the coauthors of the catechism, but the project was actually the work of a team of ministers and university theologians under the watchful eye of Frederick himself. Ursinus probably served as the primary writer on the team, and Olevianus had a lesser role. The catechism was approved by a synod in Heidelberg in January 1563. A second and third German edition, each with small additions, as well as a Latin translation were published the same year in Heidelberg. The third edition was included in the Palatinate Church Order of November 15, 1563, at which time the catechism was divided into fifty-two sections or Lord's Days, so that one Lord's Day could be explained in an afternoon worship service each Sunday of the year.

The Synod of Dort approved the Heidelberg Catechism in 1619, and it soon became the most ecumenical of the Reformed catechisms and confessions. It has been translated into many European, Asian, and African languages and is still the most widely used and warmly praised catechism of the Reformation period.

The Canons of Dordrecht, the third of our forms of unity, are unique among our confessions in more than one respect.  They are the only one of our confessions which was actually composed by an ecclesiastical assembly, the great synod of 1618-’19.  Born out of internal controversy in the Reformed churches of the Netherlands which was occasioned by the rise of the Arminian heresy, the Canons are the expression of the synod’s judgment concerning the Five Points of the Remonstrance.  This also explains the fact that the Canons are divided into five chapters, maintaining the truths of sovereign predestination, particular atonement, total depravity, irresistible grace, and perseverance of saints.  Because the Canons are an answer to the Five Points of the Remonstrance, they set forth only certain aspects of the truth rather than the whole body of the truth, as do our other confessions.  For this reason also the Canons are referred to in our Formula of Subscription as “the explanation of some points” of the doctrine contained in the Heidelberg Catechism and the Confession of Faith.  

There is attached to each chapter a Rejection of Errors, which refutes various specific errors taught by the Arminians, and does so on the basis of Scripture, so that in our Canons the truth is defined negatively as well as positively.  The Canons represent a consensus of all the Reformed churches of that day.  For all the Reformed churches participated in the work of the Synod of Dordrecht; and when the Canons were completed, the foreign delegates as well as the Dutch delegates affirmed them by their signatures.  A service of thanksgiving to God followed upon the completion of the Canons, a service at which it was thankfully remembered that the Lord had preserved the Reformed churches in the midst of a life-and-death conflict, and had preserved for the churches the truth that salvation is of the Lord alone.