On the Sabbath day two male lambs a year old without blemish, and two tenth parts of an ephah of fine flour for a meal offering, mixed with oil, and its drink offering. (28:9)
The Rosh Chodesh and Yom Tov offerings all include, at a minimum, a bull, a ram, and seven lambs, in addition to a sin offering. The Shabbos offering is relatively meager, consisting only of two lambs and no sin offering. The first to notice this (according to Midrash Socher Tov as quoted in Daas Zekenim) was Shabbos herself. She complained to Hashem. He told her that this is a fitting Korban for her, since everything about Shabbos is doubled: its shir (is both רומזמ and ר יש), its enjoyment (ל תארקו תבש גנוע ' ה שו דקלמדבוכ), its punishment (ו י ת ו מ ה י ל לחמתמ), and its lechem mishneh. This is why the musaf of Shabbos is uniquely described as כרול י וא. The Midrash adds that just as Klal Yisroel has a doubled meal of “lechem mishneh” on Shabbos, so too Hashem limits his meal (ל י נ ברקי מח) to a doubling of the regular tamid.
The Daas Zekenim continues explaining the Shabbos Mussaf Tefillah at length. Some highlights: תנכת תבש – this is similar to the ןכתו םינבל that the Bnei Yisroel were required to prepare in Egypt; just as the amount of bricks were counted out, so too, the days of the week are counted out before Shabbos. היתונברק תיצר – Hashem only accepts a korban that has already gone through one Shabbos.
