§ Ainulindalë The Silmarillion

But Manwë was the brother of Melkor in the mind of Ilúvatar, and he was the chief instrument of the second theme that Ilúvatar had raised up against the discord of Melkor; and he called unto himself many spirits both greater and less, and they came down into the fields of Arda and aided Manwë, lest Melkor should hinder the fulfilment of their labour for ever, and Earth should wither ere it flowered. And Manwë said unto Melkor: 'This kingdom thou shalt not take for thine own, wrongfully, for many others have laboured here do less than thou.' And there was strife between Melkor and the other Valar; and for that time Melkor withdrew and departed to other regions and did there what he would; but he did not put the desire of the Kingdom of Arda from his heart.