There are many examples of thematic quotes in Emily Brontë's Wuthering Heights.
Passion and Love: in Chapter Nine, Catherine is speaking to Nellie of her feelings for Heathcliff, and why she cannot marry him. She also speaks to her lack of love for Edgar Linton.
'I've no more business to marry Edgar Linton than I have to be in heaven; and if the wicked man in there [Hindley] had not brought Heathcliff so low, I shouldn't have thought of it. It would degrade me to marry Heathcliff now; so he shall never know I love him: and that, not because he's handsome, Nelly, but he's more myself than I am. Whatever our souls are made of, his and mine are the same; and Linton's is as different as a moonbeam from lightning, or frost from fire.'
Cruelty (also in Chapter Nine):
[Hindley] entered, vociferating oaths dreadful to hear; and caught me in the act of stowing his son away in the kitchen cupboard...and the poor thing remained perfectly quiet wherever I chose to put him.
'There I'e found it out at last!' cried Hindley, pulling me back by the skin of my neck, like a dog. 'By heaven and hell, you've sworn between you to murder that child!...But with the help of Satan, I shall make you swallow the carving-knife...I want to kill some of you: I shall have no rest until I do!...
'...I see that hideous little villain is not Hareton: I beg your pardon, Nell. If it be, he deserves flaying alive for not running to welcome me, for screaming as if I were a goblin...Kiss me, Hareton! Damn thee, kiss me! By God, as if I would rear such a monster! As sure as I'm living, I'll break the brat's neck.'
Poor Hareton was squalling and kicking his father's arms with all his might, and redoubled his yells when he carried him up-stairs and lifted him over the bannister...
Hindley actually drops the child inadvertently, but Heathcliff, providentially, just happens into the spot below—unaware of the difficulty—until a child falls into his arms.
In Chapter Three, after Mr. Earnshaw has died, Hindley has become the "lord" of the manner, returning with his wife. He is cruel to both his sister Catherine, and his "foster brother" Heathcliff.
'Poor Heathcliff! Hindley calls him a vagabond, and won't let him sit with us, nor eat with us any more; and, he says, he and I must not play together, and threatens to turn him out of the house if we break his orders. He has been blaming our father (how dare he?) For treating H. too liberally; and swears he will reduce him to his right place—'
Supernatural: in Chapter Thirty-Four, reports of seeing Heathcliff's ghost, and "a woman," abound in the area where he lived and died.
But the country folk, if you ask them, would swear on the Bible that he walks: there are those who speak to having met him near the church, and on the moor, and even within this house...that old man by the kitchen fire affirms he has seen two on 'em looking out of his chamber window on every rainy night since his death...
...I encountered a little boy with sheep and two lambs before him; he was crying terribly; ...'What's the matter, my little man?' I asked.
'There's Heathcliff and a woman yonder, under t' nab,' he blubbered, 'un' I darnut pass 'em.'
I saw nothing...
The quotations provided are what actually represent the themes you have identified: passion and love, cruelty, class conflict and the supernatural. There are, of course others—such as "revenge" and "nature," but these provide a well-rounded glimpse of the story's plot.