When Moses failed to come back down the mountain right away, the people went to Aaron. "Look," they said, "make us some gods who can lead us. This man Moses, who brought us here from Egypt, has disappeared. We don't know what has happened to him."
So Aaron said, "Tell your wives and sons and daughters to take off their gold earrings, and then bring them to me."
All the people obeyed Aaron and brought him their gold earrings.
Then Aaron took the gold, melted it down, and molded and tooled it into the shape of a calf. The people exclaimed, "O Israel, these are the gods who brought you out of Egypt!"
When Aaron saw how excited the people were about it, he built an altar in front of the calf and announced, "Tomorrow there will be a festival to the LORD!"
So the people got up early the next morning to sacrifice burnt offerings and peace offerings. After this, they celebrated with feasting and drinking, and indulged themselves in pagan revelry.
Then the LORD told Moses, "Quick! Go down the mountain! The people you brought from Egypt have defiled themselves.
They have already turned from the way I commanded them to live. They have made an idol shaped like a calf, and they have worshiped and sacrificed to it. They are saying, 'These are your gods, O Israel, who brought you out of Egypt.'"
Then the LORD said, "I have seen how stubborn and rebellious these people are.
Now leave me alone so my anger can blaze against them and destroy them all. Then I will make you, Moses, into a great nation instead of them."
But Moses pleaded with the LORD his God not to do it. "O LORD!" he exclaimed. "Why are you so angry with your own people whom you brought from the land of Egypt with such great power and mighty acts?
The Egyptians will say, 'God tricked them into coming to the mountains so he could kill them and wipe them from the face of the earth.' Turn away from your fierce anger. Change your mind about this terrible disaster you are planning against your people!
Remember your covenant with your servants -- Abraham, Isaac, and Jacob. You swore by your own self, 'I will make your descendants as numerous as the stars of heaven. Yes, I will give them all of this land that I have promised to your descendants, and they will possess it forever.'"
References for Exodus 32:13
So the LORD withdrew his threat and didn't bring against his people the disaster he had threatened.