Be careful, or you will be enticed to turn away and worship other gods and bow down to them. Then the LORD’s anger will burn against you, and he will shut the heavens so that it will not rain and the ground will yield no produce, and you will soon perish from the good land the LORD is giving you. (Deuteronomy 11:16–17, NIV)
God speaks most strictly about man’s making and serving idols.
The first and second of the Ten Commandments introduced in Exodus 20 are both about the command not to make any form of an idol or serve other gods before the Lord. He warned that if they bow down to idols or worship them, He would punish the children and their children for the sin of the fathers to the third and fourth generation.
Revelation 21:8 also warns that all idolaters will be thrown into the fiery lake of burning sulfur, which will be the second death. The reason God hates idols is apparent. God is the Creator of all things and humans. In the Bible, God has said many times that there is no god other than God. However, if man serves creatures more than the Creator who created themselves, it is glorifying them not God, and loving them more than God. Thus, the holy wrath of the Lord must burn fiercely against them.
Idolatry is to worship and serve creations rather than the Creator, as recorded in Romans 1:25.
One of the reasons people serve creations is that they are visible, and they mistakenly believe that they would be more helpful. That is why they are more dependent on creations rather than God.
In the Bible, many cases verify that people served idols for this reason. When the Philistines invaded Israel, Saul, the first king of Israel, got so frightened that he went to a young shaman and asked her to summon the dead Samuel to know the result of the battle. He finally met the soul of Samuel through the spiritual medium of the shaman. However, he had heard only curses from the dead Samuel and eventually died in the war while he was running away. It is recorded in 1 Chronicles 10 that one of the reasons Saul died was that he relied on the shaman without asking God, so the Lord killed him.
In 2 Chronicles 16, when Baasha, king of Israel, invaded Judah, Asa, king of Judah, took the gold and silver out of the treasuries of the Lord’s temple and his palace to send them to Ben-Hadad, king of Aram, and ask for help. However, God described relying on the king of Aram as a foolish act. The Lord said what he had counted on would leave him and he would have another war from then.
In Isaiah 31, the people of Israel relied on the mighty military power of Egypt to overcome the king of Assyria. Seeing this, the Lord said that the Egyptians were only man, not God, and their horses were only flesh, not spirit. And the Lord added that both Israel and Egypt would perish together because of it. To rely on the creations that you see because you cannot see God through your eyes means denying the living God and also ignoring the mighty Lord. That is idolatry.