Amos was not a prophet (holy man). Amos looked after sheep. But God sent Amos with a message to his nation (Amos 7:14-15).
Amos knew that many nations were evil. Because of these evil deeds, God would punish the nations (Amos chapters 1-2).
But Amos's own nation, Israel, was also evil. They were cruel to poor people. The judges were not fair in court. And they served evil gods. Amos warned his people that they must confess their evil deeds to God. And they must learn to do the right things (Amos 5). Otherwise, God would allow Israel's enemies to attack (Amos chapters 6-9). And these enemies would destroy the nation.
But God would not always punish the people from Israel. After these terrible punishments, God would allow some of the people to return to their own land (Amos 9:11-15).
The Book of Amos is in the Bible (Old Testament).