סימן קצו סעיף ב
אוֹנֵן, פָּטוּר מִכָּל הַמִצְוֹת שֶׁבַּתּוֹרָה, וַאֲפִלּוּ אִם אֵינוֹ צָרִיךְ לַעֲסֹק בְּצָרְכֵי הַמֵּת, כְּגוֹן שֶׁיֶשׁ לוֹ אֲחֵרִים שֶׁעוֹסְקִים בִּשְׁבִילוֹ. וַאֲפִלּוּ אִם רוֹצֶה לְהַחְמִיר עַל עַצְמוֹ, אֵינוֹ רַשַּׁאי, מִפְּנֵי כְּבוֹד הַמֵּת. אֵינוֹ מְבָרֵךְ לֹא הַמּוֹצִיא וְלֹא בִּרְכַּת הַמָּזוֹן. וַאֲפִילוּ אִם אֲחֵרִים אוֹכְלִין וּמְבָרְכִין, אֵינוֹ עוֹנֶה אָמֵן. וְאֵינוֹ מִצְטָרֵף לֹא לַזִּמוּן וְלֹא לַעֲשָׂרָה. אֲבָל מַה שֶׁהוּא מִצְוַת לֹא תַעֲשֶׂה, אֲפִילּוּ מִדְּרַבָּנָן, אָסוּר גַּם לוֹ. וְלָכֵן אִם בָּא לֶאֱכֹל פַּת, צָרִיךְ לִטּוֹל יָדָיו, וְלֹא יְבָרֵךְ עַל נְטִילַת יָדָיִם, כְּמוֹ שֶׁאֵינוֹ מְבָרֵךְ הַמּוֹצִיא. וְכֵן בִּנְטִילַת יָדַיִם שַׁחֲרִית נוֹטֵל יָדָיו שָׁלֹשׁ פְּעָמִים כְּדַרְכּוֹ, וְאֵינוֹ מְבָרֵךְ (עַיֵּן בהלכות אונן להגאון מוהרא"ז מרגליות זצ"ל אות ו).
An onein is exempt4The period of onein lasts until the deceased has been covered with earth. Once the attendants begin throwing earth on the body, the mourner should immediately go into a house or building on the cemetery and say Kerias Shema and Shemoneh Esrei. (Mishnah Berurah 71:2) from all mitzvos of the Torah, even if it is not necessary for him to be occupied with the arrangements for the deceased, as he has others to do so in his behalf. Even if he wants to be stringent [and perform mitzvos] he is not permitted to do so,5If he said Kerias Shema etc. while he was an onein, he did not fulfil his obligation and must repeat his prayers after the burial (Ibid 71:3). out of respect to the deceased.6When there are others who are occupied with the burial arrangements, the son is permitted to go to the synagogue to say Kaddish, as this is a mark of respect. This is certainly true on Shabbos and Yom Tov when there is no burial. (Mishna Berurah 71:7) He should not say the berachah of Hamotzei on bread nor recite Birkas Hamazon after eating. Even if others eat and recite berachos, he should not respond Amein [to their berachos]. He cannot be included in a quorum of three for Birkas Hamazon, or in quorum of ten (a minyan) for prayers. However, prohibitory mitzvos, even those enacted by the Sages, are forbidden even to an onein. Therefore if he wants to eat bread, he must wash his hands, but he must not say the berachah, Al Netilas Yadayim, just as he must not say the Hamotzi. Regarding the washing of hands upon arising in the morning, he should wash his three times as customary but without saying the berachah.
תנא דבי אליהו כל השונה הלכות בכל יום מובטח לו שהוא בן העולם הבא שנאמר הליכות עולם לו אל תקרי הליכות אלא הלכות (נדה ע"ג.)