sources mekorot - Dogs in Judaism

I've heard that dogs are somewhat special in Judaism. For example, I heard that the word "כלב" (dog) comes from "לב" (heart), and it means something like "loved one". I also once heard that G-d gave Cain a dog to protect himself (I think) when he became a wanderer. And I also heard that the dogs didn't bark when the firstborns were killed in Egypt.

Are the things that I mentioned true? What are the sources? Are dogs special or different in a way from the other animals according to Judaism?

Answer

I heard that the word "כלב" (dog) comes from "לב" (heart), and it means something like "loved one".

Actually it's closer to like a heart indicating that dogs tend to be loyal friends. Or as the Aish Hatorah site says:

The notable sixteenth century Jewish leader, the Maharsha, says that a dog is a creature of love. Hence, the Hebrew name for a dog is "kelev" which is etymologically derived from the words "kulo lev" or "all heart" (Rabbi Shmuel Eidels, Chidushei Aggadot, Sanhedrin 97a).

I also once heard that G-d gave Cain a dog to protect himself (I think) when he became a wanderer.

This is in the Medrash, in Breishis Raba 22:12:

רַב אָמַר כֶּלֶב מָסַר לוֹ

The Ramban elaborates on it.

ובבראשית רבה (כב יב) אמרו כענין זה רבי אבא אמר כלב מסר לו כי מפני שהיה פחדו מן החיות מסר לו אחת מהן שתלך לפניו ולמקום שיפנה הכלב ללכת ידע כי שם צוה לו השם ולא יהרג בה

That he was given a dog as he was afraid the animals would kill him, so he was given one fo them to show him the way, and wherever it went he then knew it was ordained by Hashem and he wouldn't be killed there.

And I also heard that the dogs didn't bark when the firstborns were killed in Egypt.

This is an explicit verse in Shemot 11:7

וּלְכֹל בְּנֵי יִשְׂרָאֵל לֹא יֶחֱרַץ כֶּלֶב לְשֹׁנוֹ לְמֵאִישׁ וְעַד בְּהֵמָה

And for all the Jews, no dog would bark, from man to animal...

Are the things that I mentioned true? What are the sources?

Yes. See above.

Are dogs special or different in a way from the other animals according to Judaism?

As a reward for not barking, the Torah commands us to give the dogs those dead animals that are not Kosher to eat. (Shemot 22:30)

בָשָׂר בַּשָּׂדֶה טְרֵפָה לֹא תֹאכֵלוּ לַכֶּלֶב תַּשְׁלִכוּן אֹתוֹ

There is also a Halacha that one may feed a stray dog on Shabbat. (But not any other stray animal.) (Kitzur Shulchan Aruch 87:18)

נוֹתְנִין מְזוֹנוֹת לִפְנֵי כֶּלֶב. וַאֲפִלּוּ שֶׁל הֶפְקֵר, יֵשׁ קְצָת מִצְוָה לִתֵּן לוֹ מְעַט מְזוֹנוֹת, שֶׁהֲרֵי הַקָּדוֹשׁ בָּרוּךְ הוּא חַס עָלָיו עַל שֶׁמְּזוֹנוֹתָיו מוּעָטִין, וּמַשְׁהֶה אֲכִילָתוֹ בְּמֵעָיו שְׁלשָׁה יָמִים.

Dogs are also used as the classic test to decide if something is edible, when it's relevant. Is it fit for a dog to eat is an expression found often in Halacha.

That said, the Halacha is that one may not own a vicious dog. See Kitzur Shulchan Aruch 190:2:

וְכֵן כָּל מִכְשׁוֹל שֶׁיֶשׁ בּוֹ סַכָּנַת נְפָשׁוֹת, מִצְוַת עֲשֵׂה לַהֲסִירוֹ וּלְהִשָׁמֵר מִמֶּנּוּ וּלְהִזָּהֵר בַּדָּבָר יָפֶה, שֶׁנֶּאֱמַר, הִשָּׁמֶר לְךָ וּשְׁמֹר נַפְשְׁךָ מְאֹד. וְאִם הִנִּיחַ וְלֹא הֵסִיר אֶת הַמִּכְשׁוֹלִים הַמְבִיאִים לִידֵי סַכָּנָה, בִּטֵּל מִצְוַת עֲשֵׂה וְעָבַר בְּלֹא תָשִׂים דָּמִים, כְּגוֹן אִם סֻלָּם רָעוּעַ עוֹמֵד בְּבֵיתוֹ וַחֲצֵרוֹ, וְכֵן הַמְגַדֵּל כֶּלֶב רָע.