Aaron places his hands on the head of the goat. This symbolically represents the transferring of the sins of the people to the animal. In this instance, he places both hands on the creature as an emphatic act (see further Leviticus 1:4; Leviticus 3:2; Leviticus 4:4). According to Ross, Aaron laid both hands on the goat in order to ensure the transference of sin to the goat.
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21 And Aaron shall lay both his hands on the head of the live goat, and confess over it all the iniquities of the people of Israel, and all their transgressions, all their sins. And he shall put them on the head of the goat and send it away into the wilderness by the hand of a man who is in readiness.