Amos is the book of the herdsman from Tekoa, a small town in Judah. He receives a direct call from God to prophesy against the unrighteousness of both Judah and Israel. Amos is the first prophet to proclaim that God is the ruler of the whole world.

Amos 4

4:8 So two or three cities wandered unto one city, to drink water; but they were not satisfied: yet have ye not returned unto me, saith the LORD.