§ Of Beren and Lúthien The Silmarillion

Then at last Melian spoke, and she said to Thingol: 'O King, you have devised cunning counsel. But if my eyes have not lost their sight, it is ill for you, whether Beren fail in his errand, or achieve it. For you have doom either your daughter, or yourself. And now is Doriath drawn within the fate of a mightier realm.' But Thingol answered: 'I sell not to Elves or Men those whom I love and cherish above all treasure. And if there were hope or fear that Beren should come ever back alive to Menegroth, he should not have looked again upon the light of heaven, though I had sworn it.'