Va'etchanan - R'vi'i
Ten Times Two
Moshe convened the people for a review of the Ten Commandments, which God gave the nation at Sinai. They are: (1) To recognize God; (2) Not to worship idols; (3) Not to take God's Name in vain; (4) To keep Shabbos; (5) To honor one's parents; (6) Not to murder; (7) Not to commit adultery; (8) Not to steal; (9) Not to perjure; (10) Not to covet.
Cross-reference this list with the account found in parshas Yisro, Exodus chapter 20, and you'll find some minor variations. Perhaps most striking is that there it says to remember Shabbos (zachor) and here it says to guard Shabbos (shamor). The former refers to the things we do to sanctify Shabbos, such as making kiddush, while the latter refers to the labors from which we abstain. The two commandments are significant in other ways; the two Sabbath candles that are traditionally lit correspond to these two phrases. (See Talmud Shavuos 20b for the simultaneous utterance of these commands, as alluded to in the singing of “Lecha Dodi” on Friday nights.)