Only one is found who is worthy to open the scroll, the Lion of Judah, the Root of David, the Lamb who was slain. This symbolism is not explained, because the Scripture has already explained it (The Throne and the Lamb, pg. 18).

The Lion of the tribe of Judah:

Judah is a lion’s whelp;
From the prey, my son, you have gone up.
He bows down, he lies down as a lion;
And as a lion, who shall rouse him? Gen 49:9.

For it is evident that our Lord arose from Judah, of which tribe Moses spoke nothing concerning priesthood. Heb 7:14.

The Root of David:

There shall come forth a Rod from the stem of Jesse,
And a Branch shall grow out of his roots.

“And in that day there shall be a Root of Jesse,
Who shall stand as a banner to the people;
For the Gentiles shall seek Him,
And His resting place shall be glorious.” Isa 11:1, 10.

And again, Isaiah says:
“There shall be a root of Jesse;
And He who shall rise to reign over the Gentiles,
In Him the Gentiles shall hope.” Rom 15:12.

“I, Jesus, have sent My angel to testify to you these things in the churches. I am the Root and the Offspring of David, the Bright and Morning Star.” Rev 22:16.

Elements throughout Revelation mirror elements and visions the other Old Testament prophets have seen, which ties this prophecy to theirs (The Throne and the Lamb, pg. 16).

The cross references in the NASB are especially helpful for references back to the Old Testament prophets.

We shall see that all the events of the history to come are contained in the scroll, for the seventh seal contains seven trumpets, and the seventh trumpet contains seven bowls of wrath … so the scroll contains seals, trumpets, and bowls. (The Throne and the Lamb, pg. 17).

“As the seventh seal contains the seven trumpets, and the trumpets must therefore be designed to follow after all the first six seals in time, then the design of the book continues, showing the seventh trumpet contains all of the seven bowls of woe. Therefore, as comprising the seventh trumpet, the seven bowls of woe must all be after the first six trumpets … The scheme of the book is to understand the symbols in sequence of order and of time.”

Fred Miller, Revelation: A Panorama of the Gospel Age, Ch. 1, “The Plan and Design of Revelation.”

Is the Lord here teaching, that a person’s name is entered into the Book of Life by grace through faith, but then can be blotted out by (lack of) works, by not enduring or remaining faithful to the end? Smarter people than I have debated that … (The Letters to the Seven Churches, pg. 13).

The theological terms for the doctrines of eternal and conditional salvation, are monergism, and synergism. Monergism “is the position in Christian theology that God, through the Holy Spirit, works to bring about the salvation of individuals through spiritual regeneration without cooperation from the individual.” Since the Holy Spirit is the agent of salvation and not the individual, salvation is not conditional, but eternal. Synergism is “the belief that God and individuals cooperate for salvation.” Since the individual cooperates in his salvation, his salvation can be conditional.

“Monergism,” Wikipedia.

“Pelagius and Augustine, in whom these opposite forms of monergism are embodied, are representative men, even more strictly than Arius and Athanathius before them, or Nestorius and Cyril after them. … They represented principles and tendencies, which, in various modifications, extend through the whole history of the church, and reappear in its successive epochs. The Gottschalk controversy in the ninth century, the Reformation, the synergistic controversy in the Lutheran church, the Arminian in the Reformed, and the Janenistic in the Roman Catholic, only reproduce the same great contest in new and specific aspects.”

Philip Schaff, History of the Christian Church, Vol. 3, pp. 786-787.