במדבר, פרק כ״ח, פסוק כ״ב

During the festival of Passover, a specific goat is brought as a sin offering to bring purity to the people. The purpose of this atonement addresses different types of shortcomings. It serves to clear the Israelites of any accidental impurity they may have brought into the Sanctuary over the course of the previous year [ביאור שטיינזלץ]. Alternatively, the atonement is directly tied to the festival itself, meant to make up for any spiritual stumbles that naturally occur amid the busy crowds and commotion of the holiday [העמק דבר].

A deeper look reveals a contrast between this offering and the sin offering brought on the new moon. On the new moon, the nation is only present at the Sanctuary in a spiritual sense. Because they are not physically gathered, their everyday flaws remain somewhat hidden, and that offering is simply dedicated to God. On Passover, however, the entire nation physically gathers at the Sanctuary. This massive human presence puts everyone's natural flaws on full display, making the need for personal cleansing much more obvious. For this reason, the Passover offering emphasizes that the atonement is made directly for the people themselves [רש ר הירש].

Beyond the specific details of this offering, the Torah keeps its overall description of the sacrifices for the seven days of Passover quite brief, leaving out a full list of the burnt offerings. This shortened account relies entirely on the Oral Torah, which carries the complete, detailed tradition of the sacrifices and serves as an essential companion to the written text [אבן עזרא].