Exodus 32:2
1 When the people saw that Moses delayed in coming down from the mountain, they gathered around Aaron and said to him, “Get up, make us gods that will go before us. As for this fellow Moses, the man who brought us up from the land of Egypt, we do not know what has become of him!” 2 So Aaron said to them, “Break off the gold earrings that are on the ears of your wives, your sons, and your daughters, and bring them to me.” 3 So all the people broke off the gold earrings that were on their ears and brought them to Aaron. 4 He accepted the gold from them, fashioned it with an engraving tool, and made a molten calf. Then they said, “These are your gods, O Israel, who brought you up out of Egypt.”
Pseudo Philo Biblical Antiquities 12:2
2 But while he was in the mount, the heart of the people was corrupted, and they came together to Aaron saying: Make us gods that we may serve them, as the other nations also have. For this Moses by whom the wonders were done before us, is taken from us. And Aaron said unto them: Have patience, for Moses will come and bring judgement near to us, and light up a law for us, and set forth from his mouth the great excellency of God, and appoint judgements unto our people.
Notes and References
"... God reported to [Moses] the astounding news: the people had 'gone astray' in his absence and made for themselves a golden calf to worship. Unbelievable as this might appear, still more incredible was the fact that the Bible attributes to Aaron, Moses' own brother, a central role in the incident ... These verses make it seem as if Aaron had quite willingly supplied the people with an idol to worship—in fact, he even seems to have taken the initiative after hearing the people's complaint. But why? Had not Moses left Aaron in charge of things during his absence? ... It seemed to interpreters most unlikely that God should select someone who had willingly encouraged the people to idolatry. For all such reasons, interpreters theorized that Aaron had not taken the initiative in the golden calf incident, nor even simply submitted to the people's request. He must have done something first to try to stop them, and if the Bible did not say so specifically, perhaps it was simply because his opposition proved ineffective ..."
Kugel, James L. The Bible as it Was (p. 423) Harvard University Press, 1998