Quotes

 "If you made a better rat than a human, that's not much to boast about." - Sirius Black: 'Harry Potter & the Prisoner of Azkaban'

 "To the well-organized mind, death is but the next great adventure." - Albus Dumbledore: "Harry Potter and the Philosophers Stone"

 "Fear of a name increases fear of a thing itself." - Albus Dumbledore: "Harry Potter and the Philosophers Stone"

 "Longbottom, if brains were gold, then you'd be poorer than Weasley, and that would be saying something." - Draco Malfoy: 'Harry Potter & the Philosopher's Stone'

 "What happened between you [Harry Potter] and Quirrel down through the trapdoor is a complete secret, so, naturally, the whole school knows." - Albus Dumbledore: 'Harry Potter & the Philosopher's Stone'

 "I can make that old bloke down there pick his nose again, and again, and again..." - Ron Weasley: "Harry Potter and the Goblet of Fire"

 "Never trust anything that can think for itself if you can't see where it keeps its brain." - Arthur Weasley: "Harry Potter and the Chamber of Secrets"

 "...which one of you will be dying this year?" - Minerva McGonagall: "Harry Potter and the Prisoner of Azkaban"

 "Humans have a knack for choosing precisely the things that are worst for them." - Albus Dumbledore: "Harry Potter and the Philosophers Stone"

 "...it matters not what someone is born, but what they grow to be!" - Albus Dumbledore: "Harry Potter and the Goblet of Fire"

 "Cedric Diggory was murdered by Lord Voldemort." - Albus Dumbledore: "Harry Potter and the Goblet of Fire"

 "There is a stench of guilt upon the air." - Voldemort: "Harry Potter and the Goblet of Fire"

 "It is my belief...that the truth is generally preferable to lies..." - Albus Dumbledore: "Harry Potter and the Goblet of Fire"

 "Differences of habit and language are nothing at all if our aims are identical and our hearts are open." - Albus Dumbledore: "Harry Potter and the Goblet of Fire"

 "...this is no time to be a gentleman! Knock her off her broom if you have to!" - Oliver Wood: "Harry Potter and the Prisioner Of Azkaban"

 "Voldemort...is my past, present, and future." - Tom Marvolo Riddle (Voldemort): "Harry Potter and the Chamber of Secrets"

 "I haven't blushed so much since Madam Pomfrey told me she liked my new earmuffs." - Albus Dumbledore: "Harry Potter and the Philosophers Stone"

 "Bone of the father, unknowingly given, you will renew your son...Flesh of the servant, willingly given, you will revive your master...Blood of the enemy, forcibly taken, you will resurrect your foe." - Peter Pettigrew: "Harry Potter and the Prisioner of Azkaban"

 "How many will be brave enough to return once they feel it?" - Voldemort: "Harry Potter and the Goblet of Fire"

 "Listen to me, reliving family history...why, I am growing quite sentimental!..." - Voldemort: "Harry Potter and the Goblet of Fire"

 "...we are only strong as we are united, weak as we are divided..." - Albus Dumbledore

 "Oh, Rita hasn't written anything at all since the third task...As a matter of fact, Rita Skeeter isn't going to be writing anything at all for a while..." - Hermione Granger: 'Harry Potter & the Goblet of Fire'

 "He [Draco Malfoy] seems to have sprouted little tentacles all over his face. Well, let's not leave them here, they don't add much to the decor." - George Weasley: 'Harry Potter & the Goblet of Fire'
 ''..I thought it (The Triwizard tornament egg) sounded a bit like Percy singing... maybe you have to attack him when he is in the shower, Harry." - George Weasley: 'Harry Potter & the Goblet of Fire'

Credits to UK Harry Potter