"Holy, holy, holy is the Lord God Almighty, who was, and is, and is to come." (Revelation 4:8)
After the seven letters, a door stands open in heaven and the voice says: come up here and I will show you what must take place after this. At once John is in the Spirit before the throne of God. The vision is deliberately evocative of Isaiah 6 and Ezekiel 1, the great Old Testament throne-room visions, but it surpasses them both. The one seated on the throne has the appearance of jasper and ruby. A rainbow that shines like an emerald encircles the throne. From the throne come flashes of lightning, rumblings, and peals of thunder. Before the throne is what looks like a sea of glass, clear as crystal. Around the throne are four living creatures: like a lion, like an ox, like a man, and like a flying eagle, each with six wings and covered with eyes, crying without ceasing: Holy, holy, holy is the Lord God Almighty, who was, and is, and is to come.
Whenever the living creatures give glory and honour and thanks to the one on the throne, the twenty-four elders fall down before him and cast their crowns before the throne, saying: you are worthy, our Lord and God, to receive glory and honour and power, for you created all things, and by your will they were created and have their being. The Catechism calls this vision the model of all Christian liturgy: every Eucharist is a participation in this heavenly worship, a joining of the earthly assembly to the unceasing praise of the four living creatures and the twenty-four elders (CCC 1137).
Brothers and sisters, the living creatures do not rest day or night, saying holy, holy, holy. This is the permanent activity of heaven: the unceasing adoration of the one who is, and was, and is to come. Every Sunday Mass is an entry into this room. Every Eucharist is a moment of singing with the four living creatures. You are not watching worship from outside; you are participating in the worship that never stops. Come to Mass with that awareness.
Holy, holy, holy Lord God Almighty, who was and is and is to come. You are worthy to receive glory and honour and power, for you created all things and by your will they were created and have their being. We cast our crowns before your throne. Through Christ our Lord. Amen.