Commentaire sur Le Deutéronome 5:18

ולא תתאוה — The Targum renders this by ולא תירוג which, too, is an expression denoting “desiring” (חמד the word used in the preceding part of this verse), just as (Genesis 2:9) “נחמד to the eyes”, we render in the Targum by “desirable (רגג) to behold”.

ולא תחמוד , “and you shall not covet, etc.” In Parshat Yitro the commandment employs only the verb תמד, whereas here Moses added an additional phrase commencing with the verb אוה, to desire (in the reflexive mode). From the wording in Yitro we would have thought that only when steps are taken to translate one’s burning desire into practice does one transgress this prohibition. If Moses had not added the dimension of merely “desiring” a field, or an ox, we might have thought, that only when one engages in translating one’s desire into practice is this prohibited, but that “daydreaming” about it is not objectionable. Hence, he restated part of the original version to make the point we just mentioned.

ולא תתאוה בית רעיך, “and do not covet the house of your fellow.” In the first version of the Ten Commandments the Torah described this coveting of one’s fellow’s house with the verb לא תחמוד. The difference is whether one is planning to pay for it or wants it even without contemplating paying for it i.e. not planning to translate his craving into action. Here Moses reminds us that even the mere thought of wanting it makes one liable for violating this commandment. The reason is that ultimately the desire to own what belongs to someone else (who has not offered it for sale) will lead to one offering money and pressuring the owner to part with it (compare Maimonides Hilchot Gezeilah 1,9).