Idolatry means the worship of or giving reverence to anything or anyone before the true and living God. This includes the worship of idols that may replace the God of Abraham.

God told Jonah to go to Nineveh and tell the people to get their act together because they were serving other gods. Jonah did not want to go in the beginning and went a different route. After going through a great ordeal for disobeying God, Jonah finally went and told the Ninevites and they repented and turned back to God and he forgave them (Jonah 2).

When Jeremiah spoke to the people of Judah and Jerusalem about their false worshipping as their forefathers did, God basically turned his back on them when they cried out to him. He told them to cry out to the gods whom they worshipped gave incense to (Jeremiah 22).

Isaiah told the people that they did not care who they took into battle with them to include their wooden idols. Isaiah let them know they were dealing with a god that cannot save them. The Almighty God had taken care of Jacob up to the present (Isaiah 45).

In the book of Hosea the more the prophets talk to the people, the more they would go out and worship their gods .They continued sacrificing to the Baals and burning incense to the graven images (Hosea 11).

Micah tells the people that God will cut off the carved images and the statues or pillars out of their midst. He also would destroy their cities and their Asherim. God would cut off their witchcraft, their horses and chariots (Micah 6).

In Malachi the people had married to foreign Gods and was faithless for an abomination had been committed in Israel. They had profaned the holy sanctuary of the Lord which He loves. And with double guilt they covered the altar with their tears because the Lord does not regard their offering anymore (Malachi).

In the book of Amos the people would burn a sacrifice of thanksgiving of that which is leavened which was highly forbidden. For all this God withheld the rain just before their crops were ready to harvest. He allowed it to rain in some areas and not in others. The places it did not rain, the people suffered a great loss (Amos 4).
God was not pleased with the social injustice of His people. So he put rules and ordinances in place to prevent and rectify this.

Isaiah told the people to seek justice and do what is right in the sight of God. If someone did wrong they needed to be dealt with and whoever was oppressed needed to be taken care of also. If people would come and reason together although their sins are like scarlet, they shall be white as snow although they are red like crimson. If you do well you will eat the good of the land. If you refuse and rebel, you will be devoured by the sword. (Isaiah chapter 1)

Zechariah told the people to execute true judgment and show mercy and kindness and tender compassion every man to his brother. Do not oppress the widow or the fatherless, the temporary resident or the poor, and let none of you devise or imagine or think evil against his brother in your heart (Zechariah 7).

Execute justice and righteousness, and deliver out of the hand of the oppressor him who has been robbed and do no wrong, do no violence to the stranger or temporary resident, the fatherless, or widow, nor shed innocent blood in this place (Jeremiah 22).

He has showed you, O man, what is good. And what does the Lord require of you but to do justly, and to love kindness and mercy, and to humble yourself and walk humbly with your God (Micah 6)?

Therefore because you tread upon the poor and take from him exactions of wheat, you have built houses of hewn stone but you shall not dwell in them: you have planted pleasant vineyards, but you shall not drink their wine. (Amos 5).

As I live, says the Lord God, Sodom your sister has not done, her nor her daughters, as you have done, you and your daughters. Behold, this was the iniquity of your sister Sodom: pride, overabundance of food, prosperous ease, and idleness was hers and her daughters. (Ezekiel 16)

Then I will draw near to you for judgment: I will be a swift witness against the sorcerers, against the adulterers, against the false swearers, and against those who oppress the hireling in his wages, the widow and the fatherless, and who turn aside the temporary resident from his right and fear not Me says the Lord of hosts (Malachi 3).

Throughout the Old Testament the prophets would constantly tell the people that God wanted a relationship with them. It was ok to offer sacrifices and offerings to God but not to the other Gods. The people would always take things out of the context. They would start out alright but would always play to close to the edge. Then they would eventually fall into the wrong hands. The prophets let them know that serving God was a serious thing and not to be taken for granted. God had put forth his laws with no room for variations. The people would always get into a comfort zone and end up messing up. All of the above apply to us today. God just want a relationship with us. He wants us to be obedient and give him and only him the respect that He deserves for being our Father.