Maimonides is Yom Basar’s intellectual godfather.
Mishneh Torah, Rest on a Holiday 6:18
(18) The children, for example, should be given parched grain, nuts, and sweetmeats; the womenfolk should be presented with pretty clothes and trinkets according to one’s means; the menfolk should eat meat and drink wine, for there is no real rejoicing without the use of meat and wine.
The essence of Yom Basar!
Pesachim 49b:3
תַּנְיָא, רַבִּי אוֹמֵר: עַם הָאָרֶץ אָסוּר לֶאֱכוֹל בְּשַׂר, (בְּהֵמָה) שֶׁנֶּאֱמַר: ״זֹאת תּוֹרַת הַבְּהֵמָה וְהָעוֹף״: כׇּל הָעוֹסֵק בַּתּוֹרָה מוּתָּר לֶאֱכוֹל בְּשַׂר בְּהֵמָה וָעוֹף.
It was taught in a baraita that Rabbi Yehuda HaNasi says: It is prohibited for an ignoramus to eat meat, as it is stated: “This is the law [torah] of the beast and of the fowl” (Leviticus 11:46). He expounds: Anyone who engages in Torah study is permitted to eat the meat of animals and fowl.
Some simple guidelines
Deuteronomy 14:3-6
לֹ֥א תֹאכַ֖ל כׇּל־תּוֹעֵבָֽה׃ זֹ֥את הַבְּהֵמָ֖ה אֲשֶׁ֣ר תֹּאכֵ֑לוּ שׁ֕וֹר שֵׂ֥ה כְשָׂבִ֖ים וְשֵׂ֥ה עִזִּֽים׃ אַיָּ֥ל וּצְבִ֖י וְיַחְמ֑וּר וְאַקּ֥וֹ וְדִישֹׁ֖ן וּתְא֥וֹ וָזָֽמֶר׃ וְכׇל־בְּהֵמָ֞ה מַפְרֶ֣סֶת פַּרְסָ֗ה וְשֹׁסַ֤עַת שֶׁ֙סַע֙ שְׁתֵּ֣י פְרָס֔וֹת מַעֲלַ֥ת גֵּרָ֖ה בַּבְּהֵמָ֑ה אֹתָ֖הּ תֹּאכֵֽלוּ׃
You shall not eat anything abhorrent. These are the animals that you may eat: the ox, the sheep, and the goat; the deer, the gazelle, the roebuck, the wild goat, the ibex, the antelope, the mountain sheep, and any other animal that has true hoofs which are cleft in two and brings up the cud—such you may eat.
Deuteronomy 12:20
כִּֽי־יַרְחִיב֩ יְהֹוָ֨ה אֱלֹהֶ֥יךָ אֶֽת־גְּבֻלְךָ֮ כַּאֲשֶׁ֣ר דִּבֶּר־לָךְ֒ וְאָמַרְתָּ֙ אֹכְלָ֣ה בָשָׂ֔ר כִּֽי־תְאַוֶּ֥ה נַפְשְׁךָ֖ לֶאֱכֹ֣ל בָּשָׂ֑ר בְּכׇל־אַוַּ֥ת נַפְשְׁךָ֖ תֹּאכַ֥ל בָּשָֽׂר׃
When יהוה enlarges your territory, as promised, and you say, “I shall eat some meat,” for you have the urge to eat meat, you may eat meat whenever you wish.
Ben Yehoyada on Pesachim 109a:3
It seems to me that, with God’s help, happiness must be complete for both body and soul, meaning that the body enjoys eating meat and the soul enjoys identifying the holy sparks that appear from eating the meat…
Numbers 11:4
(4) The riffraff in their midst felt a gluttonous craving; and then the Israelites wept and said, “If only we had meat to eat!
Sifrei Devarim 75:4
“and you will say: I shall eat flesh, for your soul will desire to eat flesh”
Shulchan Arukh, Orach Chayim 250:2
(2) A person should have more meat, wine and treats, to the best of his ability.
Mishnah Chullin 3:7
(7) And with regard to grasshoppers, whose signs were also not stated in the Torah, the Sages stated: Any grasshopper that has four legs, and four wings, and two additional jumping legs, and whose wings cover most of its body, is kosher. – Grasshoppers should not be consumed at Yom Basar at this time. A t’shuvah is forthcoming.
Shabbat 129b:2
רַב וּשְׁמוּאֵל דְּאָמְרִי תַּרְוַיְיהוּ: הַאי מַאן דְּעָבֵיד מִילְּתָא — לִישְׁהֵי פּוּרְתָּא וַהֲדַר לֵיקוּם — דְּאָמַר מָר: חֲמִשָּׁה דְּבָרִים קְרוֹבִין לְמִיתָה יוֹתֵר מִן הַחַיִּים, וְאֵלּוּ הֵן: אָכַל וְעָמַד, שָׁתָה וְעָמַד, יָשֵׁן וְעָמַד, הִקִּיז דָּם וְעָמַד, שִׁימֵּשׁ מִטָּתוֹ וְעָמַד.
It was Rav and Shmuel who both said: With regard to one who performs the practice of bloodletting, let him wait a bit and then let him rise, as the Master said: There are five matters that render one closer to death than life, and they are these: If one ate and immediately rose, if one drank and rose, if one slept and immediately rose, if one let blood and rose, if one engaged in conjugal relations and rose.
Sanhedrin 59b:13-14
אמר רב יהודה אמר רב אדם הראשון לא הותר לו בשר לאכילה
Rav Yehuda says that Rav says: Meat was not permitted to Adam, the first man, for consumption.