Before John, the writer of Revelation, saw the seven seals, he first saw a scene, a view, in the heavens (Rev. 4:2-3; 5:1-7; 6:1-17; 8:1-2). This scene in heaven was immediately after Christ’s ascension into the heavens (see Rev. 5:6, note 3—Recovery Version).
In this scene there was a throne, and God was sitting upon the throne (Rev. 4:2-3).
On the right hand of God, who sat upon the throne, was a scroll sealed with seven seals (Rev. 5:1). The scroll is a record of the secret of God’s economy concerning the entire universe.
John wept because there was no one in heaven or on the earth or under the earth who was able, worthy, to open the scroll and to break its seals (Rev. 5:2-4).
Then he was told not to weep because the Lion of the tribe of Judah, the Root of David, the Lamb, had overcome to open the scroll and its seven seals. This One came and took the scroll out of the right hand of God, who sat upon the throne, and He opened one of the seven seals (Rev. 5:5-7; 6:1).
The Lion is a symbol of Christ, portraying Him as a strong fighter against the enemy, as prophesied in Genesis 49:8-9. Christ’s being the Root of David signifies that He is the source of David. When the Lord was living on earth, the Pharisees asked Him questions to test Him. Then the Lord asked them a question to silence them. He asked, "What do you think concerning the Christ? Whose Son is He?" (Matt. 22:42). When they answered that Christ was David’s son, He replied, "How then does David in spirit call Him Lord, saying, The Lord said to My Lord, Sit on My right hand until I put Your enemies underneath Your feet? If then David calls Him Lord, how is He his Son?" (Matt. 22:43-45). This muzzled the mouths of all His opposers. Christ is not only the Son of David, the Branch of David (Jer. 23:5; 33:15), but also the Lord of David, the Root of David. As a descendant of David in His humanity, Christ is the Branch of David who issued out of David. But as the eternal God in His divinity, Christ is the Root of David, the source of David. Christ is also our redeeming Lamb in this present age. As such an all-inclusive One, He has overcome to open the scroll and its seven seals.
(The Prophecy of the Four 'Sevens' in the Bible, Chapter 2, by Witness Lee)