The foundational text is Shemot 16:22–30, which records that God gave Israel a double portion of bread on the sixth day precisely because the seventh day is a holy sabbath of rest, commanding the people to bake and boil on Friday and to lay up what remained — explaining the arrangement as God's own gift: "it is GOD who, having given you the sabbath, therefore gives you two days' food on the sixth day."
Bereshit Rabbah 11:2 draws the explicit connection between this narrative and the sanctification of Shabbat itself, teaching in the name of Rabbi Yishmael that God blessed the seventh day through the manna — blessing it in that a double omer fell on Erev Shabbat — and sanctified it through the manna in that no manna fell on Shabbat at all.
The Mekhilta reads the verse "and on the sixth day they shall prepare" (Mekhilta DeRabbi Yishmael, Tractate Vayassa 3:5) as a source that a person should make preparations from Erev Shabbat for Shabbat, and it further distinguishes the word מִשְׁנֶה as meaning bread that was qualitatively changed — distinct in character — separate from the plain doubling in quantity spelled out elsewhere.
Rashi on Shemot 16:22 records a midrashic reading that לֶחֶם מִשְׁנֶה means changed bread — מְשֻׁנֶּה — that on Erev Shabbat the manna was changed for the better in its smell and taste, and the Malbim on Shemot 16:5 develops this further, arguing that the heavenly preparation of a double portion signaled that Shabbat's holiness infused the manna with a superior quality, so that the earthly act of preparation below mirrored a corresponding sanctification above.
Shabbat 117b derives from "and on the sixth day they shall prepare what they bring" that a person must rise early on Friday morning to prepare for Shabbat — Rav Chisda reads the juxtaposition of preparing and bringing as requiring immediate action at daybreak — and further derives from the double portion the obligation to break bread at every Shabbat meal over two loaves, leḥem mishneh.
Peninei Halakhah, Shabbat 7:3 explains that the two loaves at each Shabbat meal are specifically a commemoration of the double manna that fell on Fridays, and notes that the doubling pervades Shabbat entirely — its commandments, its sacrifices, its reward and punishment — so that the bread itself expresses the doubled greatness of the day.
Rashi on Shemot 16:5 understands the doubling as a divine blessing in the home — the portion measured out was found to be double what was normally gathered — and Ibn Ezra on Shemot 16:5 confirms that מִשְׁנֶה simply means two omers per person as stated in the text.
The Ramban on Shemot 16:23 explains the instruction to bake and boil on Friday as a directive to do all cooking for both days on the sixth day, setting aside the remainder for Shabbat morning, and when the people saw the next day that the leftover manna had not spoiled, Moses permitted them to eat it — the miracle of preservation itself teaching that Shabbat rest is divinely sustained.
Tur, Orach Chayim 250 and Shulchan Arukh, Orach Chayim 250:1 codify the practical consequence: a person must rise early on Friday morning to prepare Shabbat's needs, and even one attended by many servants should personally do something in Shabbat's honor — citing the Amoraim who chopped wood, lit fires, and arranged the house as models — because this personal effort is itself the honor of Shabbat.
Shulchan Arukh HaRav, Orach Chayim 250 adds that even after preparing in the morning it is a mitzva to prepare again at twilight, finding a hint in the word מִשְׁנֶה itself — understood as "a second time" — so that the double preparation on Friday mirrors and honors the double portion of manna.
Mishnah Berurah 250:2 records the practice of Shammai the Elder, who honored Shabbat by selecting fine food all week and setting it aside, finding his authority in the verse "remember the Shabbat day to sanctify it" — understood as a call to designate beautiful things for Shabbat whenever they come to hand throughout the week.
Peninei Halakhah, Shabbat 2:2 synthesizes the tradition, stating that while some preparation is fitting all week, the primary time is Friday morning, just as in the wilderness Israel gathered immediately at dawn on the sixth day, and notes that the admirable custom of women baking challah on Friday morning directly reenacts the manna-gathering that inaugurated the institution of Shabbat preparation.
Sefat Emet, Shemot, Beshalach 24:3 presses further into the theological significance, teaching that Moses told Israel the essence of eating the manna was in Shabbat — not that Shabbat was a subtraction from the manna because none fell, but the reverse: Shabbat is the very root of the manna, and Bnei Yissaschar, Shabbatot 3:3 connects this to the Zohar's teaching that Shabbat's food derives from a higher source than the manna of the weekdays, which is why no manna fell on Shabbat at all — the double portion on Friday being the earthly expression of that supernal bounty.
Finally, Shabbat 118b frames the stakes of the entire institution: had Israel properly observed the first Shabbat commanded through the manna narrative, no foreign nation would ever have ruled them, and Rabbi Yohanan in the name of Rabbi Shimon bar Yohai teaches that if Israel were to observe two Shabbatot fully, redemption would come immediately — anchoring the double portion not only as a practical preparation but as the paradigm of Shabbat's cosmic significance.
