§ Of the Coming of the Elves and the Captivity of Melkor The Silmarillion

But when the Battle was ended and from the ruin of the North great clouds arose and hid the stars, the Valar drew Melkor back to Valinor, bound hand and foot, and blindfold; and he was brought to the Ring of Doom. There he lay upon his face before the feet of Manwë and sued for pardon; but his prayer was denied, and he was cast into prison in the fastness of Mandos, whence none can escape, neither Vala, nor Elf, nor mortal Man. Vast and strong are those halls, and they were built in the west of the land of Aman. There was Melkor doomed to abide for three ages long, before his cause should be tried anew, or he should plead again for pardon.