“Seek good, not evil, that you may live. Then the LORD God Almighty will be with you, just as you say he is. Hate evil, love good; maintain justice in the courts. Perhaps the LORD God Almighty will have mercy on the remnant of Joseph.” -Amos 5:14-15
Amos was before Isaiah and influenced some of what the later prophets did. Amos was not raised in the Prophet community and held them in contempt. He was an outsider aware of the contemptible trade in money for prophecy, in much the same way Martin Luther would be. Amos called for reform.
Amos called for social justice. God was not impressed with institutionalised oppression. Amos saw God as the almighty, God everywhere, not solely his chosen. Amos saw that God was ethical, preferring righteousness to ceremony.
Amos saw divine judgement for the faults of Israel and Judah. He was exiled for his message. What Amos foresaw came true. And God fixed the problems with Jesus in a way that Amos foresaw, but few understood. Seek good, not evil, that you may live.