This is a very famous commandment from God’s Ten Commandments. We have all heard over and over again that we shall not have idols in our lives.
Exodus 20:1-6 1And God spoke all these words, saying, 2 “I am the Lord your God, who brought you out of the land of Egypt, out of the house of slavery. 3 “You shall have no other gods before me.
It’s so important because our God is a jealous God
Exodus 20: 4 “You shall not make for yourself a carved image, or any likeness of anything that is in heaven above, or that is in the earth beneath, or that is in the water under the earth. 5 You shall not bow down to them or serve them, for I the Lord your God am a jealous God, visiting the iniquity of the fathers on the children to the third and the fourth generation of those who hate me, 6 but showing steadfast love to thousands of those who love me and keep my commandments.
If a married man flirts with another woman or affair with another woman, and his wife is not jealous, you would wonder if his wife has either given up with him or planning to divorce him. That’s because love is jealous and possessive. If our God is not jealous and possessive over us, then He is truly not in love with us. God has used very lovers language in the song of songs, and also in numerous OT prophecies regarding his hate for Israel’s rampant idolatry like a wild woman laying bare to men. To say that God is not jealous when we stray from him, is not reading the Bible.
There are reasons why God makes such a strong claim and an exclusive demand on Israel and us
Because the Lord our God is the one who brought Israel out of the slavery and bondage of Egypt.
Now this is a very important point because that gives God the credibility, authority to claim basically us as his possession. Because God delivered the 3 millions Jews out of the slavery cruelty imposed by Pharaoh, the greatest powerful king at that time, in the land. God worked mighty miracles one after the other to deliver Israel from the fierce power of the throne of Pharaoh. God sent plagues after plagues like turned Nile to blood, sent locusts to devour all of Egypt farms, sent darkness over all Egypt, killed all the first born of Egypt including the prince of pharaoh , and finally God hardened Pharaoh’s heart to pursue Israel when clearly the divine power was with Moses to lead them out of Egypt. God to top it up, divided the Red Sea, in a most stunning sight and miracle by a strong east wind, and led the 3 million Jews crossed the Red Sea on dry land, on the Red Sea bed. Can you imagine the impact of this out of the world experience of Israel, with mothers, children, young and old men and women with their cattle’s, belongings, silver and gold they plundered from Egypt walking thru the Red sea?
And this only enticed Pharaoh and his chariots foolishly followed the crowd into the Red Sea, only to find them to be drowned under the swelling currents when Israel stepped foot on dry ground, when God withdrew the east wind and closed the Red Sea. Pharaoh and army all died and their corpses all appeared on the beach the next day, and when Israel saw these corpses on the beach, the bowed down and worshipped the Lord.
Exodus 14:30–31 30 Thus the Lord saved Israel that day from the hand of the Egyptians, and Israel saw the Egyptians dead on the seashore. 31 Israel saw the great power that the Lord used against the Egyptians, so the people feared the Lord, and they believed in the Lord and in his servant Moses.
This may sound too much even for a Hollywood movie, and I agree, in fact God is the best director ever, more than any of the Hollywood. And He pulled it off! Egypt was bowed done and they saw the might of the God of Israel displayed as they mourned their dead first born children.
And what about us today? God has delivered you from your self indulgent sinful life of depravity by bringing you from the kingdom of darkness into the kingdom of light by his own Son Jesus Christ died on the cross as a substitute redemption! Thats why He makes such bold claim of allegiance. In fact, His claim is for our well being and flourishing, as God created us to enjoy and flourish in Christ! And He prepared an eternity we will spend with our triune God for ever and ever in the coming world, in heaven!
That’s why God can say what he says, no other gods before me. For our utmost well-being, and no more in the life of slavery bondage to our sins and powers of darkness.
Not just Carved Images
But just exactly what is an idol? In my childhood days of my growing up as a Christian, I always relate to those carved image, like animal etc. (Ex 20:4) and I could never figure that out. I have never seen anyone bowed down to a bird, lion, tiger?? I have seen people using jo-sticks with incense bowing before idols of men like some imagery sculpture of some beings, that’s was scaring to me as a kid. That was my experience seeing those Chinese temples where people throng to during festive seasons in Malaysia. My grandma (father side) definitely insisted on worshipping ancestors which was abhorred by my mum, a Christian with Methodist church, causing tension between her and her mother in law. Thank God for my mum! She would fight to keep her children, like me her first born, away from any food that’s been offered to idols by my grandma. She zealously protectively covered her children from such idolatry.
If we desire something or someone more than God, that’s an idol
But now as I am exposed to more reformed teaching like Tim Keller spoke a lot on idolatry that’s in our hearts. It’s more like an imagery allegiance to some force or attractions or stability formed by culture and human cravings essentially.
It’s always been taught that if we desire something or someone more than God, that’s an idol. But how do we measure it? On way is when what or who we desire exceeds our desire for God. Particularly clear is when we desire something or someone that’s contrary to the will of God as explained explicitly in the Bible. That will be a clear case of idolatry. You see idolatry in that case can surface and go away depending on time and season of your life. Example, if you put your heart so much into your job that’s consuming your time, energy, to the extent of sacrificing your own time with your family, and also in worshipping God and serving God in your ministry, that intense job will be questionable and probably be put in the category of ‘idols’.
Our Idol is really our creation of a god that will give us our desires
I read this article by Benjamin Gladd that catches my eyes on this statement: “Israel continues this idolatrous pattern, desiring to worship a god, the golden calf, who would give them what they desired rather than waiting for the true God to tell them what he desired.” 
Israel made a golden calf as their god when Moses was up in Mt Sinai 40 days receiving the Ten Commandments from God. In their loss of patience and confidence in Yahweh, the God who brought them out of the slavery of Egypt by such might and power, they succumbed to their depraved fallen desire fleshly wants. The made a golden calf, and Gladd expounded well to say that this gold calf would give them what they desire. That’s the best definition of idiolatry. Idols can’t think, can’t talk, they just receive your requests petitions and instructions. That’s the ultimate machine for you to tell exactly what you want from this idol. That defines idolatry. It’s really to fulfill your own hearts desires, nothing more than that. Because the Lor our God will listen, and rebuke, and direct and love us. Israel wanted none of that. They wanted to follow their own desires. Just like Adam and Eve when tempted, Eve wanted to fulfill her own desires, rather than God’s.
God originally put Adam in the Garden of Eden to function as king, priest, and prophet. He ruled over all the creation of God and he worshipped God and walked and talked with God. But all that collapsed when his dear wife, Eve, took the bait of the serpent, the devil, and surrendered the kingdom to Satan. That’s why we have such mess in the worlds today, and we need a savior.
Jesus came and restored humanity to their roles as obedient kings, priests, and prophets through his faithful life, which ended by taking the punishment for our idolatrous failure to do the same.
 Benjamin Gladd, Sin as Idolatry, https://www.thegospelcoalition.org/essay/sin-as-idolatry/