Quran 2:67 — The Heifer (Al-Baqarah)

Moses said to his people, "GOD commands you to sacrifice a heifer." They said, "Are you mocking us?" He said, "GOD forbid, that I should behave like the ignorant ones."

[2:66] We set them up as an example for their generation, as well as subsequent generations, and an enlightenment for the righteous.

[2:68] They said, "Call upon your Lord to show us which one." He said, "He says that she is a heifer that is neither too old, nor too young; of an intermediate age. Now, carry out what you are commanded to do."