מדרש על במדבר 28:24

(Bamidbar 28:24) "As these shall you offer each day for seven days.": Why is this written? For (were it not written) it would follow, (otherwise), viz.: Since Succoth requires a festival offering, and Pesach requires a festival offering, therefore, just as the offering of Succoth decreases progressively (each day [viz. Bamidbar 29:12-13]) so should that of Pesach decrease progressively. It is, therefore, written "As these shall you offer each day" — neither to increase or to decrease. "in addition to the continual burnt-offering shall it be offered, and its libation": We are hereby apprised that the mussafim (of Pesach) are sacrificed only between the two (temidim).