Rebbe Nachman of Breslov, Likutei Eitzot
The essence of the holiness which every person must strive for is to observe the Covenant in purity. The way to achieve this is by sanctifying the way you speak. You must speak only words of holiness and keep yourself from any lapse into language which is not holy. Then whatever you say will be in the "Holy Tongue," and through this you will achieve the holiness of the Covenant.
קדשים תהיו. הֱווּ פְרוּשִׁים מִן הָעֲרָיוֹת וּמִן הָעֲבֵרָה, שֶׁכָּל מָקוֹם שֶׁאַתָּה מוֹצֵא גֶדֶר עֶרְוָה אַתָּה מוֹצֵא קְדֻשָּׁה
You shall be holy: Separate yourselves from sexual immorality and from sin, for wherever one finds a barrier against sexual immorality, one finds holiness.
Abraham Joshua Heschel, "The meaning of observance"
To the philosophers the idea of the good was the most exalted idea, the ultimate idea. To Judaism, the idea of the good is penultimate. It cannot exist without the holy. The good is the base; the holy is the summit. Man cannot be good unless he strives to be holy.
One who is holy...clings constantly to his God (davek tamid l'elohav), his soul traveling in channels of truth, amidst the love and fear of his Creator -- such a person is as one walking before God in the land of the living, here in this world.
וְלָמָּה אֲנִי אוֹמֵר בַּמִּקְדָּשׁ וִירוּשָׁלַיִם קְדֻשָּׁה רִאשׁוֹנָה קָדְשָׁה לֶעָתִיד לָבוֹא. וּבִקְדֻשַּׁת שְׁאָר אֶרֶץ יִשְׂרָאֵל לְעִנְיַן שְׁבִיעִית וּמַעַשְׂרוֹת וְכַיּוֹצֵא בָּהֶן לֹא קָדְשָׁה לֶעָתִיד לָבוֹא. לְפִי שֶׁקְּדֻשַּׁת הַמִּקְדָּשׁ וִירוּשָׁלַיִם מִפְּנֵי הַשְּׁכִינָה וּשְׁכִינָה אֵינָהּ בְּטֵלָה. וַהֲרֵי הוּא אוֹמֵר (ויקרא כו לא) "וַהֲשִׁמּוֹתִי אֶת מִקְדְּשֵׁיכֶם" וְאָמְרוּ חֲכָמִים אַף עַל פִּי שֶׁשּׁוֹמְמִין בִּקְדֻשָּׁתָן הֵן עוֹמְדִים
Why do I say that the original consecration sanctified the Temple and Jerusalem for eternity, while in regard to the consecration of the remainder of Eretz Yisrael, in the context of the Sabbatical year, tithes, and other similar [agricultural] laws, [the original consecration] did not sanctify for eternity?
Because the sanctity of the Temple and Jerusalem stems from the Shechinah, and the Shechinah can never be nullified. Therefore, [Leviticus 26:31] states: "I will lay waste to your Sanctuaries." The Sages declared: "Even though they have been devestated, their sanctity remains."
כָּל הַמְאַבֵּד שֵׁם מִן הַשֵּׁמוֹת הַקְּדוֹשִׁים הַטְּהוֹרִים שֶׁנִּקְרָא בָּהֶם הַקָּדוֹשׁ בָּרוּךְ הוּא לוֹקֶה מִן הַתּוֹרָה. שֶׁהֲרֵי הוּא אוֹמֵר בַּעֲבוֹדַת כּוֹכָבִים (גמרא שבת קכ ב) "וְאִבַּדְתֶּם אֶת שְׁמָם מִן הַמָּקוֹם הַהוּא לֹא תַעֲשׂוּן כֵּן לַה' אֱלֹהֵיכֶם":...כָּל הַנִּטְפָּל לַשֵּׁם מִלְּפָנָיו מֻתָּר לְמָחֳקוֹ כְּגוֹן לָמֶ''ד מִלַּיהוָֹה וּבֵי''ת מִבֵּאלֹהִים וְכַיּוֹצֵא בָּהֶן אֵינָן כִּקְדֻשַּׁת הַשֵּׁם. וְכָל הַנִּטְפָּל לַשֵּׁם מֵאַחֲרָיו כְּגוֹן ךְ' שֶׁל אֱלֹהֶיךָ וְכֶ''ם שֶׁל אֱלֹהֵיכֶם וְכַיּוֹצֵא בָּהֶן אֵינָם נִמְחָקִים וַהֲרֵי הֵם כִּשְׁאָר אוֹתִיּוֹת שֶׁל שֵׁם מִפְּנֵי שֶׁהַשֵּׁם מְקַדְּשָׁם. וְאַף עַל פִּי שֶׁנִּתְקַדְּשׁוּ וְאָסוּר לְמָחֳקָם הַמּוֹחֵק אֵלּוּ הָאוֹתִיּוֹת הַנִּטְפָּלוֹת אֵינוֹ לוֹקֶה. אֲבָל מַכִּין אוֹתוֹ מַכַּת מַרְדּוּת:
Whoever destroys one of the holy and pure names with which the Holy One, blessed be He, is called is liable for lashes according to Scriptural [Law]. [This punishment is given because such an act violates one of the Torah's prohibitions. The prohibition is derived as follows:] With regard to the worship of false gods, [Deuteronomy 12:3-4] states: "And you shall destroy their names from this place. Do not do this to God, your Lord." ... All [the letters] which are connected to [God's] name, [but are placed] before [the name itself] may be erased - e.g., the lamed of Lamed-Alef-Daled-Nun-Yud or the bet of B'Elohim and the like. They do not possess the same degree of holiness as [God's] name [itself]. All [the letters] which are connected to [God's] name, [but placed] after [the name itself] - e.g., the final chaf of Elohecha or the chaf and the final mem of Eloheichem, and the like may not be erased. They are considered like the other letters of [God's] name, because the name conveys holiness upon them. Although holiness is conveyed upon them and it is forbidden to erase them, nevertheless, a person who erases these letters which are connected to [God's] name is not [liable for] lashes. However, he does receive "stripes for rebelliousness."