§ Akallabêth The Silmarillion

But Ar-Pharazôn was not yet deceived, and it came into his mind that, for the better keeping of Sauron and of his oaths of fealty, he should be brought to Númenor, there to dwell as a hostage for himself and all his servants in Middle-earth. To this Sauron assented as one constrained, yet in his secret thought he received it gladly, for it chimed indeed with his desire. And Sauron passed over the sea and looked upon the land of Númenor, and on the city of Armenelos in the days of its glory, and he was astounded; but his heart within was filled the more with envy and hate.