A mourner must rend his garments upon the death of a relative, standing while doing so and tearing from the front of the garment, with different requirements for parents (tearing until the heart is exposed, in front of witnesses, with all garments torn for the full seven days) versus other deceased (a single tear kept in front for seven days, not required if changing clothes).
אָבֵל חַיָּב לִקְרֹעַ עַל מֵתוֹ שֶׁנֶּאֱמַר (ויקרא י ו) "וּבִגְדֵיכֶם לֹא תִפְרֹמוּ וְלֹא תָמֻתוּ" הָא אַחֵר חַיָּב לִפְרֹם. וְאֵין קְרִיעָה אֶלָּא מְעֻמָּד. שֶׁנֶּאֱמַר (שמואל ב יג לא) "וַיָּקָם הַמֶּלֶךְ וַיִּקְרַע אֶת בְּגָדָיו". וּמֵהֵיכָן קוֹרֵעַ. מִלְּפָנָיו. וְהַקּוֹרֵעַ מֵאַחֲרָיו אוֹ מִן הַצְּדָדִין אוֹ מִלְּמַטָּה לֹא יָצָא יְדֵי חוֹבַת קְרִיעָה. אֶלָּא כֹּהֵן גָּדוֹל שֶׁהוּא פּוֹרֵם מִלְּמַטָּה: כָּל שִׁבְעַת יְמֵי אֲבֵלוּת הַקֶּרַע לְפָנִים וְאִם בָּא לְהַחְלִיף מַחְלִיף וְאֵינוֹ קוֹרֵעַ קֶרַע אַחֵר. שֶׁכָּל קֶרַע שֶׁאֵינוֹ בִּשְׁעַת חִמּוּם אֵינוֹ קֶרַע. בַּמֶּה דְּבָרִים אֲמוּרִים בִּשְׁאָר הַמֵּתִים חוּץ מֵאָבִיו וְאִמּוֹ. אֲבָל עַל אָבִיו וְעַל אִמּוֹ קוֹרֵעַ עַד שֶׁמְּגַלֶּה אֶת לִבּוֹ. וּמַבְדִּיל שְׂפַת הַבֶּגֶד וְאֵינוֹ קוֹרֵעַ בִּכְלִי אֶלָּא בְּיָדוֹ מִבַּחוּץ בִּפְנֵי כָּל הָעָם וְקוֹרֵעַ כָּל הַבְּגָדִים שֶׁעָלָיו. וּבֶגֶד הַזֵּעָה הַדָּבוּק לִבְשָׂרוֹ אֵינוֹ מְעַכֵּב. וְאִם הֶחְלִיף בֶּגֶד אַחֵר חַיָּב לִקְרֹעַ כָּל שִׁבְעָה. וְכֵן עַל אָבִיו וְעַל אִמּוֹ חוֹלֵץ כְּתֵפוֹ וּמוֹצִיא זְרוֹעוֹ מִן הֶחָלוּק עַד שֶׁיִּתְגַּלֶּה כְּתֵפוֹ וּזְרוֹעוֹ. וְהוֹלֵךְ כָּךְ לִפְנֵי הַמִּטָּה. וְאַחַר שֶׁיִּקָּבֵר אָבִיו וְאִמּוֹ אֵינוֹ חַיָּב לַחְלֹץ:
A mourner is obligated to rend his garments for his dead, as can be derived from Leviticus 10:6: "Do not rend your garments lest you die." Implied is that others must rend their garments. One must rend one's garments only while standing, as II Samuel 13:31 states: "And the king stood and rent his garments." Where does one rend his garment? In front. If one rends his garment from the back or from the sides or from the bottom, he does not fulfill the obligation to rend his garments, with the exception of a High Priest who must rend his garment from the bottom. For the entire seven days of mourning, he keeps the tear in front of him. If he desires to change his garments, he may. He is not required to rend the second garment, for any tear that is not made at the time of emotional excitement, is not a tear. When does the above apply? With regard to other deceased persons aside from his father and mother. For his father and mother, by contrast, he must rend his garment until he reveals his heart. He must rip apart the border of the garment; he may not tear it with a utensil, and must tear it outside, in the presence of people at large. He must tear all the garments he is wearing. His underwear - i.e., the garments worn next to his flesh - need not be ripped. If he changes his clothes, he is required to rend them for all seven days. Similarly, for his father and mother, he uncovers his shoulder and takes his forearm out from his garment, revealing his shoulder and his forearm. He passes before the bier in this manner. After his father and his mother are buried, however, he is not required to uncover his shoulder.