The ministry of Amos lasted only for a short time, during the reign of Jeroboam II. Although brief, his message was much the same as other prophets before and after him: seek the Lord and live. God's patience had nearly reached its limits. Without a change of heart, the nation of Israel was doomed.
Israel was experiencing its greatest level of prosperity. But the scales were severely unbalanced: the wealthy were growing fat off the exploitations of the poor. But even worse, they believed that their affluence was a result of God's blessing, when in fact God was greatly displeased with the grave injustices His people were displaying. Still, God in His mercy desired to give every opportunity for His people to turn back to Him. His prophet Amos offered such an opportunity.
Amos began his ministry with judgment against the nations. Those that surrounded Israel would be punished for their mistreatment of God's people. First was Damascus, for waging cruel military campaigns against the people of Gilead in Israel. Then Gaza, one of the five primary cities of the Philistines. Gaza had made political alliances with Edom. Together they rose up against God's people, inflicting severe oppression many times. Amos then mentions Tyre, from the nation of Phoenicia, which also had a political alliance with Edom. Edom, the native land of Esau, Jacob's brother, continually pursued Israel without mercy.
Then Ammon gets confronted, the descendants of the incestuous relationship between Lot and one of his daughters. Ammon waged war against the people of Gilead in Israel, brutally and violently mutilating them in their attempted conquest. Moab, also descendants of the incestuous relationship between Lot and his other daughter, was another persistent and feared enemy of Israel. Moab committed an outrageous act of dishonor by burning the bones of the king of Edom. Finally, pushing the borders of judgment even closer to home, Judah is named and condemned for rejecting the Laws of God and giving themselves over to idolatry.
With every surrounding nation now on the judgment radar, God moves in on Israel. The sins of Israel were great, and named one by one. Their justice system was severely perverted, with righteous people enslaved for their debts and the poor sold as collateral for land. A man and his father both had relations with the same woman. The wealthy continued their form of worship, wearing the clothes of other men taken in pledge. They drank the wine of those punished by fines and took advantage of the downtrodden. They seduced the Nazarites to break their vows, and commanded the prophets to cease from their prophecies.
Israel committed many more sins, generation after generation, ever since they broke away from Judah hundreds of years before. But their most heinous of sins was their broken covenant with God, punishable by death.
Many times God had warned the people, either through his prophets to whom they would not listen, or through calamity and disaster to which they paid no attention. Famine, drought, locusts and mildew destroyed their crops. Plagues, fire and other pestilence were sent to Israel's wicked thresholds, but they never understood that these occurrences were a result of their rebellion and immorality.
Amos knew that God would deal harshly with Israel. He sounded the call of warning: Seek good and not evil, that you may live; so the LORD God of hosts will be with you, as you have spoken. (5:14) The Day of the Lord was coming. He was done with their blind injustices. He no longer wanted their sacrifices, or their songs of worship, or the music of their instruments. Instead, God wanted to see justice run down like water, and righteousness like a mighty stream. (5:24)
As in all the other prophetic books, Amos ends his prophecies with a message of hope: one day God will restore Israel. The captives will return, and rebuild their cities. They will live in peace in the land that God had given to them, never to be removed again. The next book in the prophetic books of the Old Testament shifts its focus to the neighboring nation of Edom, Israel's feared southern enemy. The prophet Obadiah confronts Edom for their hatred and pursuit of Israel, warning them that their own swift judgment was coming.