Why does the Musaf of Shabbos comprise only two lambs?
1.
Da'as Zekenim, Hadar Zekenim and Rosh (all citing Midrash Shochar Tov): When Shabbos complained about this, Hashem replied that, since everything about Shabbos is [written] double ? Shir, Oneg, Misah, Lechem [Mishneh] ? also its Korban should be double
1
[that of a regular day].
2
Da'as Zekenim: This can be compared to a king who commanded to make a meal for his sons. He then commanded to make a meal for himself ? just like they made for his sons.