John had introduced us to the Lamb when God sought someone able to open the scroll (Revelation 5:5). The Lamb looked as if it had been slain (= crucified) but was standing (= resurrection) and indeed was in heaven (= ascension) and so was worthy to take the scroll and open its seals (= make God’s plan for the development of his kingdom happen).
7 Let us rejoice and exult and give him the glory, for the marriage of the Lamb has come, and his Bride has made herself ready;