Heathcliff and Catherine's last meeting on Catherine's deathbed has a lot of important dialogue in this regard. It takes place in chapter 15 and Catherine tells Heathcliff that loving him has "killed" her. He replies:
"Catherine, you know that I could as soon forget you as my existence! Is it not sufficient for your infernal selfishness, that while you are at peace I shall writhe in the torments of hell?"
And, in chapter 16, after Catherine's death, Heathcliff cries,
"May she wake in torment! . . . Catherine Earnshaw, may you not rest, as long as I am living! You said I killed you--haunt me, then! . . . Oh, God! it is unutterable! I cannot live without my life! I cannot live without my soul!"