Amos 3:7
1 Listen, you Israelites, to this message that the Lord is proclaiming against you! This message is for the entire clan I brought up from the land of Egypt: 2 “I have chosen you alone from all the clans of the earth. Therefore I will punish you for all your sins.” 3 Do two walk together without having met? 4 Does a lion roar in the woods if he has not cornered his prey? Does a young lion bellow from his den if he has not caught something? 5 Does a bird swoop down into a trap on the ground if there is no bait? Does a trap spring up from the ground unless it has surely caught something? 6 If an alarm sounds in a city, do people not fear? If disaster overtakes a city, is the Lord not responsible? 7 Certainly the Sovereign Lord does nothing without first revealing his plan to his servants the prophets.
Revelation 10:7
5 Then the angel I saw standing on the sea and on the land raised his right hand to heaven 6 and swore by the one who lives forever and ever, who created heaven and what is in it, and the earth and what is in it, and the sea and what is in it, “There will be no more delay! 7 But in the days when the seventh angel is about to blow his trumpet, the mystery of God is completed, just as he has proclaimed to his servants the prophets.” 8 Then the voice I had heard from heaven began to speak to me again, “Go and take the open scroll in the hand of the angel who is standing on the sea and on the land.” 9 So I went to the angel and asked him to give me the little scroll. He said to me, “Take the scroll and eat it. It will make your stomach bitter, but it will be as sweet as honey in your mouth.”
Notes and References
"... The Greek idea of mystērion as something hidden, obscure or secret is expressed by the Hebrew word sôd and the Aramaic word rāz. Several occurrences of sôd in the Old Testament simply convey the idea of human secrets (Psalm 64:2; Proverbs 11:13; 20:19; 25:9); some prophets specify a heavenly council to which they had access and from which God’s secrets were revealed (Jeremiah 23:18; 23:22; Amos 3:7). In no case, however, is sôd translated as mystērion in the Septuagint, although it does occur several times in the Qumran literature ... In Revelation 1:20; 17:5, “mystery” connotes secret and symbolic meaning in the form of “the seven stars,” the name Babylon and a “woman” who is known only to God and/or the seer. Revelation 10:7, however, has no symbolic meaning but refers to the fact that the entire “mystery of God” has been made known to the prophets and will publicly be revealed after the seventh angel blows his trumpet. This idea is comparable to the Synoptics, where mystērion (Mark 4:11) and ta mystēria (Matthew 13:11; Luke 8:10) refer to God’s rule (“the secrets of the kingdom of God”) made known through the person and teaching of Jesus ..."
Martin, Ralph P. Dictionary of the Later New Testament & Its Developments (p. 1135) InterVarsity Press, 1997