Exodus 32:1-6 NIV
When the people saw that Moses was so long in coming down from the mountain, they gathered around Aaron and said, “Come, make us gods who will go before us. As for this fellow Moses who brought us up out of Egypt, we don’t know what has happened to him.”
Aaron answered them, “Take off the gold earrings that your wives, your sons and your daughters are wearing, and bring them to me.” So all the people took off their earrings and brought them to Aaron. He took what they handed him and made it into an idol cast in the shape of a calf, fashioning it with a tool. Then they said, “These are your gods, Israel, who brought you up out of Egypt.”
When Aaron saw this, he built an altar in front of the calf and announced, “Tomorrow there will be a festival to the LORD.” So the next day the people rose early and sacrificed burnt offerings and presented fellowship offerings. Afterward they sat down to eat and drink and got up to indulge in revelry.
NIV: New International Version