The Cow - 2:54
"Moses said to his people: "O My people, you have wronged your nafs (personality, essence, soul) by worshipping/serving the calf. Repent to your Creator and kill your nafs (ego). This is better for you in the sight of your Creator."He will forgive you. Surely He is the Accepter of repentance, the Most Merciful."
The repentance of those who served the calf:
The Heights/7:148
The people of Moses made after him a calf of ornaments, a calf with a roar, and idolized it. Did they not see that it was incapable of speaking and guiding them? They became of the wrongdoers by adopting it.
The Heights/7:149
"When they regretted what they had done and realized that they had gone astray, they said: "If our Lord does not pity us and forgive us, we shall be losers"."