90. And Harun indeed had said to them beforehand: "O my people! You are being tried in this, and verily, your Lord is (Allah) the Most Gracious, so follow me and obey my order.'' 91. They said: "We will not stop worshipping it, until Musa returns to us.''
Allah, the Exalted, informs of Harun's attempt to prohibit them from worshipping the calf and his telling them that this was only a test for them. He told them that their Lord was the Most Beneficent, Who created everything and decreed for everything its just measure. He is the Owner of the Mighty Throne, the One Who does whatever He wants.
(so follow me and obey my order.) Meaning, "Follow me in that which I am commanding you with and leave that which I forbid you from.''
(They said: "We will not stop worshipping it, until Musa returns to us.'') meaning, "We will not cease in our worship of this calf until we hear what Musa has to say about it.'' So they opposed Harun in this matter and they fought against him, nearly killing him.