Most certainly, the Heidelberg Catechism was neither the only nor the first catechism to be published.  In fact, the use of catechisms stretches all the way back to the early centuries of the Christian church.  The Reformers merely picked up this good tradition and make ample use of it.  Luther wrote his Small Catechism in 1529.  John Calvin published a catechism for the city of Geneva in 1542.  Those are only two examples.  Numerous others could be added to the list.  Also, there were many confessions produced by Reformed pastors and theologians.  Although these confessions were not intended, so directly, for the instruction of the youth and new converts, they nevertheless gave a short summary of the key doctrines found in Scripture.  As such, they were certainly helpful for teaching people of all ages.

Since there were so many catechisms and confessions produced in the sixteenth century the question naturally arises: did Ursinus and Olevianus and the rest of the authorship team compose the entire Heidelberg Catechism from scratch, or did they borrow from other catechisms or confessions?  This question is not easy to answer in precise detail.  There may be certain similarities between two catechisms, but that does not necessarily prove that one borrowed from the other.  Perhaps both relied on a third, as yet undiscovered, document.  And, if there is, indeed, some borrowing between two catechisms, it’s not always clear which borrowed from which.  Having said all that, there is every indication that the authors of the Heidelberg Catechism incorporated some of the best concepts and phrases from other catechisms.  The paragraphs below will illustrate the point.

The Heidelberg Catechism and Calvin’s Geneva Catechism (1542)

Since both Ursinus and Olevianus were familiar with the work of John Calvin (see their biographies here), it is not surprising that as younger church leaders they looked to Calvin’s wisdom and experience to set their course in various questions and answers.  For example, consider what the Heidelberg Catechism says about providence.

God's providence is His almighty and ever present power, whereby, as with His hand, He still upholds heaven and earth and all creatures, and so governs them that leaf and blade, rain and drought, fruitful and barren years, food and drink, health and sickness, riches and poverty, indeed, all things, come to us not by chance but by His fatherly hand (A. 27).

Then compare that to Calvin’s Catechism on the same topic.

It is He who sends rain and drought, hail, tempest and fair weather, fruitfulness and barrenness, health and sickness.  In short, all things are under his command… (A. 27).

It seems reasonable to assume that the authors of the Heidelberg Catechism made use of Calvin’s Catechism for LD 10.

The Heidelberg Catechism and Beza’s Brief Confession (1559)

During his studies in France, Caspar Olevianus also met Theodore Beza.  He appreciated Beza’s work and, it would seem, at one point he likely translated Beza’s Brief Confession from Latin into German.  Perhaps, somehow, elements of Beza’s confession also filtered into the Heidelberg Catechism.  Consider, for instance, the wording of LD 2.  In answering the question about whether we can obey the law perfectly, the Heidelberger answers:

No, I am inclined by nature to hate God and my neighbour (A. 5).

Notice how similar this is to Beza’s Confession which includes the following sentence:

Our [fallen] nature is so inclined to corruption that all men are vile toward God and hateful toward their neighbour (Art. 4).

The Heidelberg Catechism and Ursinus’ Minor Catechism

There is one source for the Heidelberg Catechism, though, about which we do not need to doubt.  That is Ursinus’ own small or Minor Catechism, likely written in either late 1561 or early 1562, shortly after Ursinus arrived in Heidelberg.  A couple of short comparisons from LD 1 will illustrate the point.  The Heidelberg Catechism opens in this way:

Q. What is your only comfort in life and death?  A. That I am not my own, but belong with body and soul, both in life and death, to my faithful Saviour Jesus Christ.  He has fully paid for all my sins with his precious blood and has set me free from all the power of the devil….

By comparison Ursinus’ Minor Catechism begins with these words:

Q. What is the comfort by which your heart is sustained in death as well as in life?  That God has truly pardoned all my sins because of Christ and has given me eternal life, in which I may glorify him forever. 

Similarly, the Heidelberg Catechism continues:

Q. What do you need to know in order to live and die in the joy of this comfort?  A. First, how great my sins and misery are; second, how I am delivered from all my sins and misery; third, how I am to be thankful to God for such deliverance.

And the Minor Catechism phrases it this way:

Q. What does God’s Word teach?  A. First, it shows us our misery; second, how we are delivered from it; third, what gratitude ought to be shown to God for this deliverance.

Ursinus’ Minor Catechism appears to be what we might call an initial, draft run for the Heidelberg Catechism.  The latter contains Ursinus’ more refined formulations, as well as the added insights of the other authors.

The Heidelberg Catechism and Olevianus’ A Firm Foundation

In 1567 Caspar Olevianus published a catechism called Vester Grundt, or A Firm Foundation.  This particular document may have been around as early as 1563, but then probably later on in the year.  Since the Heidelberg Catechism was published right away in the beginning of the year, on January 19, 1563, it is more likely that A Firm Foundation was Olevianus’ brief explanation of, and expansion on, some Lord’s Day of the Heidelberg Catechism.  In any case, it is hard to determine which way the relationship goes.  What is clear is that there is much overlap between the wording of A Firm Foundation and the Heidelberg Catechism.

In sum, then, the authors of the Heidelberg Catechism did not start with a blank piece of paper.  And why should they?  Others had already come to express certain scriptural truth in short, easy-to-understand sentences.  Rather than re-inventing the catechetical wheel, the authors of the Heidelberg Catechism stood on the shoulders of their forefathers and older siblings in the faith.  And, standing there, they reached even higher to produce one of the finest catechisms ever written.