In Revelation 5, John sees a vision of Almighty God seated on the throne with a book, sealed with seven seals, on his right hand. An angel issues a call to all of creation, challenging, “Who is worthy to open the scroll and break its seals?”, but “no one in heaven or on earth or under the earth was able to open the scroll or to look into it.”
The places “in heaven, “on earth,” and “under the earth,” however, are not chosen at random–in fact, this is a quotation of the 2nd commandment:
You shall not make for yourself a carved image, or any likeness of anything that is in heaven above, or that is in the earth beneath, or that is in the water under the earth.* You shall not bow down to them or serve them, for I the LORD your God am a jealous God, visiting the iniquity of the fathers on the children to the third and fourth generation of those who hate me, but showing steadfast love to thousands of those who love me and keep my commandments. (Ex. 20:4-6)
This allusion is not made for its own sake, but, in fact, the 2nd commandment is absolutely pertinent to the issue at stake in the throne room of heaven in Revelation 5: idolatry is wrong (in part) because no one and nothing in all of creation is worthy of our worship. To John, for a moment, this thought is disastrous, and he weeps loudly because no one was found worthy to open the scroll or to look into it.
But the gospel in Revelation 5 is that there is one who is worthy: Jesus Christ, the Lion of the Tribe of Judah, the Root of David, is able to open the seals because he has conquered (Rev. 5:5). Specifically, the Lion has conquered, because the Lamb was slain (5:6).
Worshiping anyone or anything else in all of creation not only detracts from the magnificent glory of the Lamb, but it also leaves the worshiper exposed by the sheer unworthiness of what he worships. The Lamb–and the Lamb alone–is worthy of our worship.
* The only apparent difference in the language here is that Exodus 20 speaks of “the water under the earth,” rather than simply what is “under the earth”; however, in Rev. 5:13, note the addition of a water reference as all creation joins to praise the Father and the Son: “And I heard every creature in heaven and on earth and under the earth and in the sea, and all that is in them, saying, ‘To him who sits on the throne and to the Lamb be blessing and honor and glory and might forever and ever!'”