יורה דעה שע״חYoreh De'ah 378

Se’if 1א׳

אָבֵל אָסוּר לֶאֱכֹל מִשֶּׁלוֹ בִּסְעֻדָּה רִאשׁוֹנָה, אֲבָל בַּשְּׁנִיָּה מֻתָּר, אֲפִלוּ בְּיוֹם רִאשׁוֹן. וּמִצְוָה עַל שְׁכֵנָיו שֶׁיַּאֲכִילוּהוּ מִשֶׁלָהֶם, כְּדֵי שֶׁלֹּא יֹאכַל מִשֶּׁלוֹ. וְיָכוֹל אֶחָד לְהַאֲכִיל אֶת חֲבֵרוֹ בִּימֵי אֶבְלוֹ, וְהוּא יַחֲזֹר גַם כֵּן וְיַאֲכִילֶנּוּ בִּימֵי אֶבְלוֹ, וּבִלְבַד שֶׁלֹּא יַתְנוּ בִּתְחִלָה.

A mourner should not eat his own food in his first meal of mourning, but may in his second, even if it's still the first day. His neighbours have a mitzva to feed him from their resources so that he won't have to eat his own food. One may feed his fellow during his period of mourning, and the fellow may then return the favour, provided they don't make this condition to begin with.

Se’if 2ב׳

אִשָּׁה שֶׁאֵרְעָהּ אֵבֶל, אֵין לַאֲנָשִׁים לְהַבְרוֹתָהּ; אֲבָל נָשִׁים מַבְרִין אוֹתָהּ. וְאִשָּׁה נְשׂוּאָה שֶׁאֵרְעָהּ אֵבֶל, אֵינָהּ יְכוֹלָה לֶאֱכֹל סְעֻדָּה רִאשׁוֹנָה מִשֶּׁל בַּעֲלָהּ. וְכֵן מִי שֶׁיֵּשׁ לוֹ סוֹפֵר אוֹ שָׂכִיר, אִם אוֹכֵל בִּשְׂכָרוֹ וְאֵרְעוֹ אֵבֶל, לֹא יֹאכַל סְעֻדָּה רִאשׁוֹנָה מִשֶּׁל בַּעַל הַבַּיִת. אֲבָל מִי שֶׁזָּן עָנִי אוֹ יָתוֹם אוֹ לִבְנוֹ וּבִתּוֹ, בְּלֹא תְּנַאי, וְאֶרְעָם אֵבֶל, יְכוֹלִים לֶאֱכֹל סְעֻדָּה רִאשׁוֹנָה מִשֶּׁל בַּעַל הַבַּיִת.

If mourning befell a woman, men should not provide the mourner's meal for her,6Sem(H). XI, 2 because it offers an occasion for sin. but women should provide her with the mourner's meal.7Asheri on the authority of R. Meir of Rothenberg. Cf. Lev. R. VI, 3 and Lam. R. IV, 10 (Buber), according to which a woman should provide the mourner’s meal for another woman in mourning. If mourning befell a married woman, she may not eat the first meal [after burial] of her husband.8Asheri ibid. For since the husband is required to feed her, the food is regarded as her own. When she provides other women with the mourner’s meal, she does not have to obtain her husband’s consent, for this is considered a small matter for which the husband’s approval is unnecessary. Ḥ.M. § 358 and supra § 248. However, if the husband refuses, she may not bring the mourner’s meal to other women. If both the husband and the wife are mourners, men are permitted to provide the mourner’s meal for both, since the meal in this case is provided mainly for the husband, and indirectly she eats too — A.H. For the same reason, one who obligated himself to feed his son and daughter-in-law or his daughter and son-in-law, and mourning befell them, the latter may not eat of his food — A.H. So too, one who has [in his employment] a scribe or a hired man, if [each of them] receives meals as his payment, and mourning befell him, he should not eat the first meal of his employer. But one who feeds a poor person or an orphan [because it is a meritorious act] or his son and daughter without any stipulation,9 supra par. 1, n. 5. Cf. B.B. 43b, RaShBaM s.v. זה שייך. and mourning befell them, — [the law is that] they may eat the first meal of the master of the house.

Se’if 3ג׳

אִם רָצָה הָאָבֵל שֶׁלֹּא לֶאֱכֹל בַּיּוֹם הָרִאשׁוֹן, מֻתָּר לֶאֱכֹל מִשֶּׁלוֹ אֲפִלוּ סְעֻדָּה רִאשׁוֹנָה. הַגָּה: וְכֵן אִם לֹא הִבְרוּהוּ בְּיוֹם רִאשׁוֹן שֶׁנִּמְשַׁךְ עַד הַלַּיְלָה, מֻתָּר לֶאֱכֹל בַּלַּיְלָה מִשֶּׁלּוֹ, וְאֵין צָרִיךְ הַבְרָאָה (טוּר בְּשֵׁם רֹב הַפּוֹסְקִים).

If the mourner desires not to eat on the first day,10Derived from Y.Ber. III, 1(6a) according to the reading of Tur and N in T.H. Cur. edd. of Y. have a different reading. This means that if the mourner desires to fast on the first day, he is permitted (BaḤ) — ShaK. Or Zaru’a, however, rules that the mourner is not permitted to fast unless it is a public fast day, and during the days of Penitence (עשרת ימי תשובה) even if it is his custom to fast, he is not permitted to do so, for it is a religious duty to eat the mourner’s meal — A.H. Cf. M.Abr. to O.Ḥ. § 581, n. 12 and Ba’er Heteb. he may eat of his own11e., on the second day or on the night following the first day, even if it is his first meal — ShaK. even the first meal. Gloss: So too, if he was not provided with the mourner's meal on the first day until12Lit. ‘which extended to.’ the night, he is permitted to eat at night of his own13On the same principle as supra n. 10. and he is not required to be provided with the mourner's meal.14Tur on the authority of the majority of the Codifiers — G. If the burial took place at night, the mourner’s meal is provided at night, and if he did not eat at night he is provided with same on the following day, for the day follows the night. Isserles’ ruling applies only if the mourner’s meal was not provided during the day after burial for the reasons mentioned above — P.Tesh. If the burial took place late Friday afternoon, and there was not sufficient time to provide the mourner’s meal, it must be provided Saturday night — Birke Yos.