The description of the strong angel, the cloud clothing (as when Christ ascended to heaven), the rainbow, his cry like a lion's roar, making the seven thunders speak, his oath by God the creator, and His declaration that the two witnesses were his own (11:3), indicate that he was the Lord Jesus himself, called the Angel of the LORD in the Old Testament (Exo.3:2-18,Isa.31:4, Jer.25:30, Hos.11:10, Joel 3:16, Amos 1:2).
Placing his right foot over the sea and his left over the earth, he indicates ownership over the planet. What he shouted and the seven thunders spoke John heard and understood, but it was for his benefit only, as he was not allowed to write it down for us (2Cor.12:2-4). The voice of God at times sounds like thunder to human ears (John 12:28-29).
The angel's oath is similar to that witnessed by Daniel (Dan.12:7), also probably made by the Lord Jesus, except that this time he says there will be no more delay: God's prophecies will now be fulfilled. The mystery of God is the revelation of obscure and still unsubstantiated prophecies by Daniel and other prophets.
It is improbable that this little booklet, or scroll, is the same scroll opened by the Lamb in the previous chapters. It is most likely to be like the one given to Ezekiel (Eze.2:8-3:14), which contained prophecies, words of lament, and mourning and woe, about his people, the nation of Israel. It is sweet in his mouth, for it reveals the coming victory of Christ and his millennial kingdom, but bitter in his stomach because of the suffering to come before it is accomplished.
In the light of the ending of Daniel's prophecy, it has to do with the events taking place and affecting the nation of Israel during the second half of the tribulation period, the last of the times of the Gentiles. John also still had to prophecy more about the Gentiles.
The Mighty Angel with the Little Book
1 I saw still another mighty angel coming down from heaven, clothed with a cloud. And a rainbow was on his head, his face was like the sun, and his feet like pillars of fire.
2 He had a little book open in his hand. And he set his right foot on the sea and his left foot on the land,
3 and cried with a loud voice, as when a lion roars. When he cried out, seven thunders uttered their voices.
4 Now when the seven thunders uttered their voices, I was about to write; but I heard a voice from heaven saying to me, "Seal up the things which the seven thunders uttered, and do not write them."
5 The angel whom I saw standing on the sea and on the land raised up his hand to heaven
6 and swore by Him who lives forever and ever, who created heaven and the things that are in it, the earth and the things that are in it, and the sea and the things that are in it, that there should be delay no longer,
7 but in the days of the sounding of the seventh angel, when he is about to sound, the mystery of God would be finished, as He declared to His servants the prophets.
John Eats the Little Book
8 Then the voice which I heard from heaven spoke to me again and said, "Go, take the little book which is open in the hand of the angel who stands on the sea and on the earth."
9 So I went to the angel and said to him, "Give me the little book." And he said to me, "Take and eat it; and it will make your stomach bitter, but it will be as sweet as honey in your mouth."
10 Then I took the little book out of the angel's hand and ate it, and it was as sweet as honey in my mouth. But when I had eaten it, my stomach became bitter.
11 And he said to me, "You must prophesy again about many peoples, nations, tongues, and kings."
Rev 10:1-11 (NKJV)