Leviticus 16:5

And he shall take of the congregation of the children of Israel, as the joint offering of the entire people, and therefore supplied by them, two kids of the goats for a sin-offering and one ram for a burnt offering. Although the ritual dealt with the two young goats in an entirely different manner, yet they both together constituted a single sin-offering. Thus the sacrificial victims both for the priesthood and for the congregation were provided.