Return *his* dress?

Question

After the command to return a lost ox, we find: "You should do likewise for his dress (לשמלתו)."

However, two pesukim later, we see וְלֹא-יִלְבַּשׁ גֶּבֶר שִׂמְלַת אִשָּׁה (and a man shouldn't wear a woman's dress) — apparently, a dress is an exclusively female piece of clothing. If so, why didn't it say in the pasuk about returning lost things "You should do likewise for her dress?"

The answer is not that it is coming to teach you that you have to return something even when done in transgression, or anything along those lines, because Sifri (224) learns from the example of the dress to include anything with symbols on it. Even if that is the case, it should have used the normal language, because it's not coming to teach you that rule.

And if you say a שמלה is not an exclusively female piece of clothing, then why does it say in the pasuk about not wearing the opposite sex's clothing "שמלה" to describe a woman's clothing but "כלי" to describe a man's?

Answer 1

See Rashi there, who cites Nazir 59a.

  ה. לֹא יִהְיֶה כְלִי גֶבֶר עַל אִשָּׁה וְלֹא יִלְבַּשׁ גֶּבֶר שִׂמְלַת אִשָּׁה כִּי תוֹעֲבַת יְ־הֹוָ־ה אֱלֹהֶיךָ כָּל עֹשֵׂה אֵלֶּה:

[trans]: A man's attire shall not be on a woman, nor may a man wear a woman's garment because whoever does these [things] is an abomination to the Lord, your God.

לא יהיה כלי גבר על אשה: שתהא דומה לאיש כדי שתלך בין האנשים, שאין זו אלא לשם ניאוף:  

[trans]: A man’s attire shall not be on a woman: making her appear like a man, thereby enabling her to go among men, for this can only be for the [purpose of] adultery. — [Nazir 59a]

ולא ילבש גבר שמלת אשה: לילך ולישב בין הנשים. דבר אחר שלא ישיר שער הערוה ושער של בית השחי:  

[trans]: nor may a man wear a woman’s garment: to go and abide among women. Another explanation: [In addition to not wearing a woman’s garment,] a man must also not remove his pubic hair or the hair of his armpits [for this is a practice exclusive to women]. — [Nazir 59a]

    כי תועבת: לא אסרה תורה אלא לבוש המביא לידי תועבה:  

[trans]: because… is an abomination: The Torah forbids only [the wearing of] clothes that would lead to abomination [i.e., immoral and illicit behavior]. — [Nazir 59a]

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First of all, men have more things than just clothing that make them look like men. False beards are one.

Furthermore, R' Eli'ezer Ben Ya'akov says (Naz., Ibid.) that it means a woman cannot brandish a man's tools of war.

Answer 2

There is no indication that שמלה refers to an exclusively women's garment. All indications are that it does not (actually as @avi pointed out it does not really even mean a garment per se); from other verses throughout the Torah and from this verse itself - if שמלה alone meant an exclusively women's garment, the verse would not need to modify שמלת אשה and would have simply stated לא ילבש גבר שמלה.

Also, the fact that the verse uses the term כלי when describing something a man wears is no proof to the contrary, because it changed another thing as well - it says לא יהיה instead of לא ילבש. It would seem that the simplest explanation is that when describing what the man wears the verse is actually being more broad than just describing the clothing he dresses in, which is the same reason it uses the term כלי and not שמלה. (Perhaps it was from here that R. Eliezer ben Yaakov inferred that it refers to a woman carrying a weapon in an exclusively male fashion, as @SethJ noted.)

Answer 3

A "כלי" is not clothing of any kind. It is a utensil or an item with a purpose. A "שמלה" is better translated as "chemise or shift" or even a smock rather than a dress, and there were certainly men and women versions of this type of clothing. Though today, these things have certainly become mostly female items.

Answer 4

However, two pesukim later, we see וְלֹא-יִלְבַּשׁ גֶּבֶר שִׂמְלַת אִשָּׁה (and a man shouldn't wear a woman's dress) — apparently, a dress is an exclusively female piece of clothing

I disagree with your logic.

וְלֹא-יִלְבַּשׁ גֶּבֶר שִׂמְלַת אִשָּׁה does not mean that a שמלה is exclusively a woman's clothing. I would understand simlah in that case to mean a garment and שמלת אישה to mean a woman's garment. Therefore, there is no contradiction saying to return a man's שמלה which is just a garment.

As for your second question, I don't have a definite answer, but @SethJ 's response above at least gives a possible reason.