So Moses continues to remain on the mountain with the Lord God. God is giving him instructions on service and worship, all of which demonstrates the separation between God and man. The sovereignty of God is demonstrated here, God has put His Spirit in men skilled to do this work.
While up on the mountain for forty days the people begin to tell Aaron to make them a god. Moses did not appear to be coming back to them. So they made a golden calf from their wives earrings and Aaron formed it with tools. Then they said, "This is your god, O Israel, who brought you up from the land of Egypt." (32:4).
They had created an idol. What is an idol? An idol is something created by man to represent God. God is Spirit, therefore He is unseen, men make idols to bow down to them because they cannot see God. What is wrong with this? " You shall not make for yourself an idol, or any likeness of what is in heaven above or on the earth beneath or in the water under the earth. You shall not worship them or serve them; for I, the Lord your God, am a jealous God, visiting the iniquity of the fathers on the children, on the third and the fourth generations of those who hate Me, but showing lovingkindness to thousands, to those who love Me and keep My commandments." (Exodus 20.4-6).
These people saw the cloud descend on Mt. Sinai, they heard God speak this Law with a voice of thunder and shake in fear because of it, so why would they then do this? Why would they make an idol after all that they had seen and heard? Jesus said, "It is the Spirit who gives life; the flesh profits nothing; the words that I have spoken to you are spirit and are life. But there are some of you who do not believe..."For this reason I have said to you, that no one can come to Me unless it has been granted him from the Father." (John 6.63-65).
New American Standard Bible. (1995). The Lockman Foundation.