Shorter Catechism Q. 43. What is the preface to the ten commandments? A. The preface to the ten commandments is in these words, I am the Lord thy God, which have brought thee out of the land of Egypt, out of the house of bondage.
Commentary: The Bible doesn’t refer to the Ten Commandments as the Ten Commandments but as the Ten Words (Ex. 34:28; Deut. 4:13). This is what “decalogue” means as it is a compound word consisting of “deca” (Greek for ten) and “logue” (Greek for word). The Ten Words or Decalogue is a better description than Ten Commandments because it includes not just commandments, but also declarations or statements (e.g. the preface), warnings, and promises. There are ten words from God, not strictly speaking ten imperatives. In fact, there are more than ten imperatives in the Ten Commandments.
Although God wrote down Ten Words, he did not enumerate them, and this has given rise to different ways of counting the Ten Commandments/Words. As our Catechism teaches, the Reformed tradition views the opening words as a preface, and begins counting the ten with “You shall have no other gods before Me.” The Jewish tradition views the preface as the first Word and combines the first and second commandments as the second Word. The Roman Catholic and Lutheran traditions combine the preface, first and second commandments and considers them as the first commandment. They also divide the tenth commandment into two commandments.
A preface is “any discourse going before a main subject to make way for it (John Thomson).” The opening words of the Ten Commandments function well as a preface because what is stated therein prepares us for what is to come and applies to everything that follows.