The Ten Commandments
The Ten Commandments or Decalogue (10 words) was given by God on Mt. Horeb (also known as Mt. Sinai) to Moses around 1280 BC. They are the core of the moral teachings of Israel and have come down to Christianity as part of Divine Revelation. The Church in commenting on the Commandments sees in them the totality of the negative and positive moral law, the things we should not do, as well as the things we should do. This is to say, they embody the entire natural law, what reason can discover of morality from the nature of the world and man. However, as St. Thomas Aquinas noted, not every society, much less every man, discovers the entire natural law, so God has revealed it in the Commandments so that it could be known with certainty by all men, of every society, and every age.
The Bible gives two versions of the Ten Commandments, in essential content identical, one in Exodus and another in Deuteronomy. The enumeration of the commandants (which is number one, which is two etc.) are traditional and neither contained in the texts nor obvious. The Catholic Church has traditionally used the Deuteronomy account and followed the division of the text given in the Septuagint, the Greek translation of the Scriptures made by second century BC Jews in Egypt and used by the early Church as its Old Testament. The Anglican Church and the Lutheran Church also use this account. The other Reformation churches use the Exodus listing, and adopted the Jewish enumeration of the Hebrew text.
The Commandants are probably best known from the traditional formulas used in catechesis.