These are two key chapters in understanding the book of Revelation. There were 6 seals that had been opened. The 7th seal consisted of 7 trumpets to be sounded. 6 of those 7 trumpets had been sounded and the 7th is about to sound. There is something very final about this 7th trumpet.
Rev 10: 6 and swore by him who lives forever and ever, who created heaven and what is in it, the earth and what is in it, and the sea and what is in it, that there would be no more delay, 7 but that in the days of the trumpet call to be sounded by the seventh angel, the mystery of God would be fulfilled, just as he announced to his servants the prophets.
This is a prediction of the very final last days before the fall of Jerusalem in 70 AD. At that time, there would be no more “delay” of fulfillment of the predictions of Jesus about the destruction of the city and the temple (Matthew 24). This is similar to the language of Hebrews 10:37 “Yet a little while, and the coming one will come and will not delay”. In 2 Peter 3, the mockers mocked the delayed fulfillment of Jesus’ predictions, but there would be a day when there would be no more delay.
The mystery of God would be finished as announced by His servants the prophets. Amos 3:7 Surely the Lord GOD does nothing Unless He reveals His secret counsel To His servants the prophets. That phrase was used several times to refer to the prophets of the Old Testament (2 Kings 17:13,23 for example). Those prophets had predicted the final fall of Jerusalem of 70 AD several times (Daniel 9:24-27; Daniel 12; Joel 3; Zephaniah 14; Isaiah 66). It was the last OT prophecy to be fulfilled. There were no OT predictions of any events to occur after 70 AD.
Luke 21 20 “But when you see Jerusalem surrounded by armies, then know that its desolation has come near. 21 Then let those who are in Judea flee to the mountains, and let those who are inside the city depart, and let not those who are out in the country enter it, 22 for these are days of vengeance, to fulfill all that is written. 23 Alas for women who are pregnant and for those who are nursing infants in those days! For there will be great distress upon the earth and wrath against this people. 24 They will fall by the edge of the sword and be led captive among all nations, and Jerusalem will be trampled underfoot by the Gentiles, until the times of the Gentiles are fulfilled.” This is so clear! All OT prophecy would be fulfilled in 70 AD.
Also, the “mystery of God would be finished” when this last predicted event would occur in 70 AD. The Greek word is musterion, something hidden, unknown. Strong adds one use: the secret counsels which govern God in dealing with the righteous, which are hidden from ungodly and wicked men but plain to the godly. What is this “mystery” that the prophets announced that would be fulfilled in 70 AD? Several NT passages refer to this mystery that had been hidden in ages prior to the NT, but that it had been revealed to men by the NT apostles and prophets. Ephesians 1:9 He made known to us the mystery of His will, according to His kind intention which He purposed in Him. 3:3 that by revelation there was made known to me the mystery, as I wrote before in brief. 4 By referring to this, when you read you can understand my insight into the mystery of Christ. 3:9 and to bring to light what is the administration of the mystery which for ages has been hidden in God who created all things; 5:32 This mystery is great; but I am speaking with reference to Christ and the church. 6:19 and pray on my behalf, that utterance may be given to me in the opening of my mouth, to make known with boldness the mystery of the gospel. Romans 16:11:25 Now to Him who is able to establish you according to my gospel and the preaching of Jesus Christ, according to the revelation of the mystery which has been kept secret for long ages past, Colossians 1:25 26 that is, the mystery which has been hidden from the past ages and generations, but has now been manifested to His saints, 27 to whom God willed to make known what is the riches of the glory of this mystery among the Gentiles, which is Christ in you, the hope of glory. 2:2 that their hearts may be encouraged, having been knit together in love, and attaining to all the wealth that comes from the full assurance of understanding, resulting in a true knowledge of God’s mystery, that is, Christ Himself. 1 Timothy 3:16 By common confession, great is the mystery of godliness: He who was revealed in the flesh, Was vindicated in the Spirit, Seen by angels, Proclaimed among the nations, Believed on in the world, Taken up in glory. Jesus referred to this as the “mysteries of the kingdom of heaven”. Matthew 13:11 Jesus answered them, “To you it has been granted to know the mysteries of the kingdom of heaven, but to them it has not been granted.
As you can see from these verses, this mystery is referred to in different ways, but the idea behind the word is clear. God had a plan from the very beginning to save sinners through His Son Jesus. 1 Peter 1:18 knowing that you were ransomed from the futile ways inherited from your forefathers, not with perishable things such as silver or gold, 19 but with the precious blood of Christ, like that of a lamb without blemish or spot. 20 He was foreknown before the foundation of the world but was made manifest in the last times for the sake of you. The prophets announced this plan with messianic predictions that they didn’t even understand. 1 Peter 1:10 Concerning this salvation, the prophets who prophesied about the grace that was to be yours searched and inquired carefully, 11 inquiring what person or time[a] the Spirit of Christ in them was indicating when he predicted the sufferings of Christ and the subsequent glories. 12 It was revealed to them that they were serving not themselves but you, in the things that have now been announced to you through those who preached the good news to you by the Holy Spirit sent from heaven, things into which angels long to look. Thus this mystery was announced but the understanding of it was hidden until God revealed it to the NT apostles, like Paul, and prophets. It was summarized by one word, “Christ”, but it also involved the salvation of Jewish and Gentile believers in the church. It was preached in the “gospel”. It included the predictions of the removal of the old temple and old Jewish covenant, replacing them with the new Jerusalem and the new covenant. Thus it included the destruction of the temple and the city in 70 AD as predicted by the prophets. The mystery centered on the cross, but wasn’t completely finished until that last event. Hebrews 9:8 The Holy Spirit is signifying this, that the way into the holy place has not yet been disclosed while the [i]outer tabernacle is still standing.
John is then told to take the little scroll from the giant angel, who is probably Jesus, and eat it. This is similar to what Ezekiel was told to do in Ezekiel 3. That little scroll contains the very last predictions as described already in chapter 10. The big scroll would be the scroll with the 7 seals, which would be all the predictions of events during the wars of the Jews from the spring of 66 AD when Titus entered the Promised Land to put down the Jewish rebellion up to the final destruction of the city and temple in the summer of 70 AD. The little scroll would just be the very last events in those predictions.