A rhetorical question is one that a person asks when he is more interested in developing his own thought about a matter than he is in seeking information. Rhetorical questions are used to express deep emotion (Job 3:11), surprise and/or joy (Luke 1:43), when one wishes to have his hearer to think more deeply about a subject (cf. Luke 11:11-13) and for many other reasons. Rhetorical questions are used quite often in the Bible, actually, and behooves the reader of the text to consider them when he comes to them, and discover why they are used in God’s word.
The angel’s question in Revelation 5:2 is probably rhetorical, and he didn’t expect a reply. In other words, he already knew no one was worthy. The purpose in asking was to emphasize that fact, and to drive it home to John and to all who would read what John recorded.
There are many examples of rhetorical questions in the Bible. Jesus, for example, used a rhetorical question to drive home a point he wanted to make in Matthew 7:9. There, he asks: “what man is there among you who, when his son asks for a loaf, will give him a stone?” Jesus didn’t expect anyone to actually reply to that question, but his point was: now that he had his listeners agreeing that they would never do such a thing, Jesus told them, well, neither would God. No doubt, people were told back then, as many are told today, be careful what you ask of God, he may give it to you—meaning he would answer our request to our hurt, but Jesus said, God isn’t like that. He looks upon our hearts, not necessarily our words, which may not entirely convey our heartfelt requests.
Another example of a rhetorical question, and I believe the reason for this one applies directly to the angel’s question in Revelation 5:2, is found in the twenty-first chapter of first Kings:
And Jezebel his wife said unto him, ‘Do you now govern the Kingdom of Israel? Arise, and eat bread and let your heart be merry: I will give you the vineyard of Naboth, the Jezreelite (1Kings 21:7).
Jezebel thought King Ahab needed to be reminded of who was ruler in Israel. Wasn’t all the power in Israel his own to use as he desired? Of course the king knew this, but Jezebel’s question simply drove the fact home. By getting the king to agree to the fact that he was the supreme ruler, she was able to make her point in a much stronger fashion. So, too, the angel in Revelation 5:2. Of course, no one in heaven nor on earth, nor even any of the wise ancients who had died were able to open the scroll and disclose its mysteries (cf. Isaiah 29:10-12), because what God has sealed remains sealed (cf. Revelation 3:7). This fact is borne out in Revelation 5:3. No one was found in heaven, on earth or anywhere else who could open the mysteries of the scroll.
When John discovered that the scroll was lying on the right side of the One seated on the throne, but no one in heaven or on earth was able to understand the mysteries recorded therein, he wept bitterly (Revelation 5:4). However, one of the twenty-four elders came to him and said “the Lion of the tribe of Judah, the root of David, had prevailed to open the book and to remove its seven seals” (Revelation 5:5), and, of course, the Lion of the tribe of Judah, and the Root of David are Messianic terms that point to Jesus. The first comes out of the Law (Genesis 49:9-10) and the other from the Prophets (Isaiah 11:1, 10), showing that the Law and the Prophets point to and are revealed in Jesus!