Introduction
MISHNA: On the eve of Passover, adjacent to minḥa time, a person may not eat until dark, so that he will be able to eat matza that night with a hearty appetite. Even the poorest of Jews should not eat the meal on Passover night until he reclines on his left side, as free and wealthy people recline when they eat. And the distributors of charity should not give a poor person less than four cups of wine for the Festival meal of Passover night. And this halakha applies even if the poor person is one of the poorest members of society and receives his food from the charity plate.
Why?
ארבע כוסות - כנגד ארבעה לשוני גאולה האמורים בגלות מצרים. והוצאתי אתכם, והצלתי אתכם, וגאלתי אתכם, ולקחתי אתכם, בפרשת וארא:
Four cups-- Due to the four "sayings of redemption" that were said in the Exodus from from Egypt. I will free you...I will deliver you...I will redeem you... [and] I will take you...
(ו) לָכֵ֞ן אֱמֹ֥ר לִבְנֵֽי־יִשְׂרָאֵ֘ל אֲנִ֣י יקוק וְהוֹצֵאתִ֣י אֶתְכֶ֗ם מִתַּ֙חַת֙ סִבְלֹ֣ת מִצְרַ֔יִם וְהִצַּלְתִּ֥י אֶתְכֶ֖ם מֵעֲבֹדָתָ֑ם וְגָאַלְתִּ֤י אֶתְכֶם֙ בִּזְר֣וֹעַ נְטוּיָ֔ה וּבִשְׁפָטִ֖ים גְּדֹלִֽים׃
(6) Say, therefore, to the Israelite people: I am the LORD. I will free you from the labors of the Egyptians and I will deliver [save] you from their bondage. I will redeem you with an outstretched arm and through extraordinary chastisements.
(ז) וְלָקַחְתִּ֨י אֶתְכֶ֥ם לִי֙ לְעָ֔ם וְהָיִ֥יתִי לָכֶ֖ם לֵֽאלֹקִ֑ים וִֽידַעְתֶּ֗ם כִּ֣י אֲנִ֤י יקוק אֱלֹ֣קֵיכֶ֔ם הַמּוֹצִ֣יא אֶתְכֶ֔ם מִתַּ֖חַת סִבְל֥וֹת מִצְרָֽיִם׃
(7) And I will take you to be My people, and I will be your God. And you shall know that I, the LORD, am your God who freed you from the labors of the Egyptians.
(יג) אֲפִלּוּ עָנִי הַמִּתְפַּרְנֵס מִן הַצְּדָקָה, יִמְכֹּר מַלְבּוּשׁוֹ אוֹ יִלְוֶה אוֹ יַשְׂכִּיר עַצְמוֹ בִּשְׁבִיל יַיִן לְד' כּוֹסוֹת.
(13) Even a poor person who is sustained through charity must sell his clothing or sell or rent himself in order to buy wine for the four cups.
How?
(ו) בְּכָל דּוֹר וָדוֹר חַיָּב אָדָם לְהַרְאוֹת אֶת עַצְמוֹ כְּאִלּוּ הוּא בְּעַצְמוֹ יָצָא עַתָּה מִשִּׁעְבּוּד מִצְרַיִם שֶׁנֶּאֱמַר (דברים ו כג) "וְאוֹתָנוּ הוֹצִיא מִשָּׁם" וְגוֹ'. וְעַל דָּבָר זֶה צִוָּה הַקָּדוֹשׁ בָּרוּךְ הוּא בַּתּוֹרָה וְזָכַרְתָּ כִּי עֶבֶד הָיִיתָ כְּלוֹמַר כְּאִלּוּ אַתָּה בְּעַצְמְךָ הָיִיתָ עֶבֶד וְיָצָאתָ לְחֵרוּת וְנִפְדֵּיתָ:
(6) In each and every generation, a man is obligated to show himself as though he himself went out now from the slavery of Egypt as it is said (Deuteronomy 6:23) "And He took us out of there, etc." and on account of this thing, the Holy One, blessed be He, commanded in the Torah "And you shall remember that you were a slave," that is to say as though you yourself were a slave and you went out to freedom and you were redeemed.
(ז) לְפִיכָךְ כְּשֶׁסּוֹעֵד אָדָם בַּלַּיְלָה הַזֶּה צָרִיךְ לֶאֱכל וְלִשְׁתּוֹת וְהוּא מֵסֵב דֶּרֶךְ חֵרוּת. וְכָל אֶחָד וְאֶחָד בֵּין אֲנָשִׁים בֵּין נָשִׁים חַיָּב לִשְׁתּוֹת בַּלַּיְלָה הַזֶּה אַרְבָּעָה כּוֹסוֹת שֶׁל יַיִן. אֵין פּוֹחֲתִין לוֹ מֵהֶם. וַאֲפִלּוּ עָנִי הַמִּתְפַּרְנֵס מִן הַצְּדָקָה לֹא יִפְחֲתוּ לוֹ מֵאַרְבָּעָה כּוֹסוֹת.
(7) Therefore, when a man has his meal on this night, he must eat and drink while reclining in a manner of freedom. And each and every man and woman is obligated to drink on this night four cups of wine. You can't have less than that. And even a poor person who is provided for with tzedakah can't have less than four cups.
ואפילו עני שבישראל לא יאכל עד שיסב: איתמר מצה צריך הסיבה מרור אין צריך הסיבה יין איתמר משמיה דרב נחמן צריך הסיבה ואיתמר משמיה דרב נחמן אין צריך הסיבה
We learned in the mishna that even the poorest of Jews should not eat until he reclines... Everyone agrees that matza requires reclining, but bitter herbs do not require reclining. With regard to wine, it was stated in the name of Rav Naḥman that wine requires reclining, and it was also stated in the name of Rav Naḥman that wine does not require reclining.
ולא פליגי הא בתרתי כסי קמאי הא בתרתי כסי בתראי אמרי לה להאי גיסא ואמרי לה להאי גיסא אמרי לה להאי גיסא תרי כסי קמאי בעו הסיבה דהשתא הוא דקא מתחלא לה חירות תרי כסי בתראי לא בעו הסיבה מאי דהוה הוה
The Gemara explains: And these two statements do not disagree with each other: This (i.e. one) statement is referring to the first two cups, and that (i.e. another) statement is referring to the last two cups. However, it was not clear which two cups require reclining according to Rav Naḥman.
The Gemara elaborates: Some say it in this manner, that the first two cups require reclining, as it is now that freedom begins. Since reclining is a sign of freedom, while discussing the exodus from Egypt it is appropriate to drink while reclining. By contrast, the last two cups do not require reclining, because what was already was [Maiy deHava Hava]. In other words, by this point one has completed the discussion of the Exodus and has reached the latter stages of the seder.
And some say it in that manner and claim that on the contrary, the last two cups require reclining, as it is at that time that there is freedom. However, the first two cups do not require reclining, as one still says: We were slaves. The Gemara concludes: Now that it was stated so, and it was stated so, i.e., there are two conflicting opinions and it cannot be proven which two cups require reclining, both these sets of cups and those require reclining.
How much?
As we find in the Mishnah Pesachim, the wording "no less than four" is used. However in the later sources, the wording "Dalet (Four) Kosot" appears. So...neeu what's the answer?
(ח) וְהֵבֵאתִ֤י אֶתְכֶם֙ אֶל־הָאָ֔רֶץ אֲשֶׁ֤ר נָשָׂ֙אתִי֙ אֶת־יָדִ֔י לָתֵ֣ת אֹתָ֔הּ לְאַבְרָהָ֥ם לְיִצְחָ֖ק וּֽלְיַעֲקֹ֑ב וְנָתַתִּ֨י אֹתָ֥הּ לָכֶ֛ם מוֹרָשָׁ֖ה אֲנִ֥י יקוק
(8) I will bring you into the land which I swore to give to Abraham, Isaac, and Jacob, and I will give it to you for a possession, I the LORD.”
ת"ר רביעי גומר עליו את ההלל ואומר[...] הלל הגדול דברי ר"ט
The Sages taught in a baraita: With regard to the fourth cup, one completes hallel (Birkat HaMazon) over it and ...[with the fifth cup]... recites the great hallel; this is the statement of Rabbi Tarfon.
"It is possible that as a compromise for this unresolved dispute regarding the obligation to drink a fifth cup, an additional cup is poured but not drunk—the above-mentioned Kos shel Eliyahu. Indeed, the Chatam Sofer notes that what we call Kos shel Eliyahu is actually in lieu of a fifth cup representing v’heiveiti.
According to the Vilna Gaon, the fifth cup is thus named because Eliyahu HaNavi is charged with coming in the future and resolving halachic disputes—including the one regarding the obligation to drink a fifth cup."
-Orthodox Union, What's the Truth about Eliyahu HaNavi at the Seder?
עֲבָדִים הָיִינוּ לְפַרְעֹה בְּמִצְרָיִם, וַיּוֹצִיאֵנוּ יקוק אֱלֹקֵינוּ מִשָּׁם בְּיָד חֲזָקָה וּבִזְרֹעַ נְטוּיָה. וְאִלּוּ לֹא הוֹצִיא הַקָּדוֹשׁ בָּרוּךְ הוּא אֶת אֲבוֹתֵינוּ מִמִּצְרָיִם, הֲרֵי אָנוּ וּבָנֵינוּ וּבְנֵי בָנֵינוּ מְשֻׁעְבָּדִים הָיִינוּ לְפַרְעֹה בְּמִצְרָיִם. וַאֲפִילוּ כֻּלָּנוּ חֲכָמִים כֻּלָּנוּ נְבוֹנִים כֻּלָּנוּ זְקֵנִים כֻּלָּנוּ יוֹדְעִים אֶת הַתּוֹרָה מִצְוָה עָלֵינוּ לְסַפֵּר בִּיצִיאַת מִצְרָיִם. וְכָל הַמַּרְבֶּה לְסַפֵּר בִּיצִיאַת מִצְרַיִם הֲרֵי זֶה מְשֻׁבָּח.
We were slaves to Pharaoh in the land of Egypt. And the Lord, our God, took us out from there with a strong hand and an outstretched forearm. And if the Holy One, blessed be He, had not taken our ancestors from Egypt, behold we and our children and our children's children would [all] be enslaved to Pharaoh in Egypt. And even if we were all sages, all discerning, all elders, all knowledgeable about the Torah, it would be a commandment upon us to tell the story of the exodus from Egypt. And anyone who adds [and spends extra time] in telling the story of the exodus from Egypt, behold he is praiseworthy.