While Moses was on Mount Sinai receiving the commands that God gave, the people became worried about whether or not he would return and they demanded that Aaron make gods to lead them.
When the people saw that Moses delayed to come down from the mountain, the people gathered themselves together to Aaron and said to him, “Up, make us gods who shall go before us. As for this Moses, the man who brought us up out of the land of Egypt, we do not know what has become of him.”
So Aaron said to them, “Take off the rings of gold that are in the ears of your wives, your sons, and your daughters, and bring them to me.” So all the people took off the rings of gold that were in their ears and brought them to Aaron. And he received the gold from their hand and fashioned it with a graving tool and made a golden calf.
And they said, “These are your gods, O Israel, who brought you up out of the land of Egypt!” When Aaron saw this, he built an altar before it.
And Aaron made a proclamation and said, “Tomorrow shall be a feast to the LORD.” And they rose up early the next day and offered burnt offerings and brought peace offerings. And the people sat down to eat and drink and rose up to play. (Exodus 32:1-6)