In step with OT sacrificial laws, John the Baptist had described Jesus as “the Lamb of God who takes away the sin of the world (John 1:29; cf. Isaiah 53:7). That he is now in heaven as a Lamb indicates that he has a history of saving accomplishments behind him.
6 And between the throne and the four living creatures and among the elders I saw a Lamb standing, as though it had been slain, with seven horns and with seven eyes, which are the seven spirits of God sent out into all the earth.