Quran 20:85 · Taha

After Moses’ departure from Egypt, Almighty God appointed a date for him to go to the same place at the foot of Mount Tur, where he had initially been awarded prophethood. Moses was required to reach this place along with his community in order to receive the Torah. But, in his enthusiasm, he proceeded quickly and reached the appointed place a few days earlier, leaving his community behind. Moses’ absence proved to be a trial for his community. Some polytheistic-minded persons in the community, led by the Samiri, took advantage of Moses’ absence to mislead the people into becoming calf worshippers, as was the common practice in Egypt in those days.