Silmarillion - J. R. R. Tolkien

Melkor was jealous of him, for Aulë was most like himself in thought and in powers; and there was long strife between them, in which Melkor ever marred or undid the works of Aulë, and Aulë grew weary in repairing the tumults and disorders of Melkor. Both, also, desired to make things of their own that should be new and unthought of by others, and delighted in the praise of their skill. But Aulë remained faithful to Eru and submitted all that he did to his will; and he did not envy the works of others, but sought and gave counsel. Whereas Melkor spent his spirit in envy and hate, until at last he could make nothing save in mockery of the thought of others, and all their works he destroyed if he could.

But when they desire to clothe themselves the Valar take upon them forms some as of male and some as of female; for that difference of temper they had even from their beginning, and it is but bodied forth in the choice of each, not made by the choice, even as with us male and female may be shown by the raiment but is not made thereby.

Now to water had that Ainu whom the Elves can Ulmo turned his thought, and of all most deeply was he instructed by Ilúvatar in music. But of the airs and winds Manwë most had pondered, who is the noblest of the Ainur. Of the fabric of Earth had Aulë thought, to whom Ilúvatar had given skin and knowledge scarce less than to Melkor; but the delight and pride of Aulë is in the deed of making, and in the thing made, and neither in possession nor in his own mastery; wherefore he gives and hoards not, and is free from care, passing ever on to some new work.

Yet it is told among the Eldar that the Valar endeavoured ever, in despite of Melkor, to rule the Earth and to prepare it for the coming of the Firstborn; and they built lands and Melkor destroyed them; valleys they delved and Melkor raised them up; mountains they carved and Melkor threw them down; seas they hollowed and Melkor spilled them; and naught might have peace or come to lasting growth, for as surely as the Valar began a labour so would Melkor undo it or corrupt it. And yet their labour was not all in vain; and though nowhere and in no work was their will and purpose wholly fulfilled, and all things were in hue and shape other than the Valar had at first intended, slowly nonetheless the Earth was fashioned and made firm. And thus was the habitation of the Children of Ilúvatar established at the last in the Deeps of Time and amidst the innumerable stars.