Jamieson, Fausset and Brown on Leviticus 16:5-10

5-10. shall take of the congregation ... two kids of the goats ... and one ram--The sacrifices were to be offered by the high priest, respectively for himself and the other priests, as well as for the people. The bullock (Le 16:3) and the goats were for sin offerings and the rams for burnt offerings. The goats, though used in different ways, constituted only one offering. They were both presented before the Lord, and the disposal of them determined by lot, which Jewish writers have thus described: The priest, placing one of the goats on his right hand and the other on his left, took his station by the altar, and cast into an urn two pieces of gold exactly similar, inscribed, the one with the words "for the Lord," and the other for "Azazel" (the scapegoat). After having well shaken them together, he put both his hands into the box and took up a lot in each: that in his right hand he put on the head of the goat which stood on his right, and that in his left he dropped on the other. In this manner the fate of each was decided.