מדרש על פסחים 7:3

13) Rebbi says: What is the intent of "And Moses declared the festivals of the L–rd to the children of Israel"? Because we learned only that the daily burnt-offering and the Paschal lamb override the Sabbath, it being written concerning them "in its appointed season," whence do we derive that the other communal offering also overrides the Sabbath? From "These shall you offer to the L–rd in your appointed seasons." But we did not hear (the same for) the omer and what is offered along with it and the two loaves and what is offered along with them. Therefore, in "And Moses declared the festivals of the L–rd to the children of Israel" Scripture established a set time ("festival" ["moadim"] = appointed times) for all of the offerings (even if the Sabbath must be overridden).