Amos 3:3-8
The prophet's work
3 If two people travel together, they have first agreed to meet together. 4 If a lion roars in the forest, it means that he has killed an animal to eat. A young lion does not shout unless he has caught something.
5 If there is no food in a trap, a bird will not fly into it. If the door of the trap closes, it means that it has caught something. 6 Also, if the people in a city hear a trumpet's sound, they become very afraid. If bad trouble comes to a city, it means that the Lord has sent it.
7 Before the Lord God decides to send trouble, he first tells his prophets about it. 8 So now the lion has roared! Everyone should be afraid! The Lord God has spoken, so his prophets must tell his message.