The answer is: Worshipping a golden calf

Exo 32:8

While Moses was hanging out with God on Mount Sinai, the children of Israel were busy brewing trouble below. Feeling a mix of impatience and uncertainty about their leader's return, they crafted a golden calf to worship, believing it would stand in as their connection to the divine. Picture a scene where just days prior, they had witnessed miraculous events, like the splitting of the Red Sea and the descent of manna from heaven. Yet, they turned to an idol—often symbolized in the ancient world as a god of fertility or prosperity.

This so-called “golden calf” episode starkly illustrates the struggle between faith and human tendencies toward doubt. It's interesting to note that the calf wasn’t created from scratch; instead, they brought valuable objects from Egypt, which raises questions about why they hadn’t learned from their past traumas there.

From a wider perspective, this incident echoes through many narratives in scripture where impatience leads to misguided choices. Theologians frequently point out how the Israelites demonstrate a recurring pattern: wonderful miracles followed by reviling moments of idolatry and doubt. Rather than creating a spiritual pathway, the calf becomes a pitfall in their journey, representing a failure to maintain faith in unseen guidance. Ultimately, this teaches us about the enduring need for resilience and trust in higher powers—an essential lesson for all seekers traveling through their own wilderness.