The Ten Commandments appear twice in the Torah. The first appearance is in Parshat Yitro, in Shemot, and the second time in Vaetchanan in Devarim.
There are several differences in the wording each time presented. There are actually seventeen more words in the commandments in Devarim. The number seventeen equals the word, “טוב,” meaning good. The word, Tov, does not appear in the first reading, because the two tablets were broken by Moshe Rabbeinu.
The Shabbat commandment also has a few differences. In the first reading, we are told to “Remember the Sabbath day to keep it holy.” In Devarim, the same verse begins with, “Observe,” or Shamor.
Another difference is that we are first told to keep Shabbat because G-d rested on the seventh day, and we must also rest. The second time, the reason given is that we were taken out of Egypt in order to be free men. The cessation of weekday activities, proves that we are truly free men.
A final difference is that in the last commandment it says, לא תחמוד, “Do not covet.” And in Devarim it says, לא תחמוד ולא תתאוה, that one should not covet and should not desire. The explanation to the additional words is that one’s coveting is bad enough that he desires what others have. But the לא תתאוה is a much worse kind of jealousy, in that he wants the object or person of his jealousy to lose what he has.
Studying the differences between the first and second appearance of the Ten Commandments is most fascinating. It helps us appreciate the depth and wisdom of the Torah.