This is one of my favorite quotes from the entire Song of Ice and Fire series. Image source here:
This quote was, unfortunately, somewhat butchered in the TV series. Here is the original scene from the book, in full (source):
“Why do you read so much?”
Tyrion looked up at the sound of the voice. Jon Snow was standing a few feet away, regarding him curiously. He closed the book on a finger and said, “Look at me and tell me what you see.”
The boy looked at him suspiciously. “Is this some kind of trick? I see you. Tyrion Lannister.”
Tyrion sighed. “You are remarkably polite for a bastard, Snow. What you see is a dwarf. You are what, twelve?”
“Fourteen,” the boy said.
“Fourteen, and you’re taller than I will ever be. My legs are short and twisted, and I walk with difficulty. I require a special saddle to keep from falling off my horse. A saddle of my own design, you may be interested to know. It was either that or ride a pony. My arms are strong enough, but again, too short. I will never make a swordsman. Had I been born a peasant, they might have left me out to die, or sold me to some slaver’s grotesquerie. Alas, I was born a Lannister of Casterly Rock, and the grotesqueries are all the poorer. Things are expected of me. My father was the Hand of the King for twenty years. My brother later killed that very same king, as it turns out, but life is full of these little ironies. My sister married the new king and my repulsive nephew will be king after him. I must do my part for the honor of my House, wouldn’t you agree? Yet how? Well, my legs may be too small for my body, but my head is too large, although I prefer to think it is just large enough for my mind. I have a realistic grasp of my own strengths and weaknesses. My mind is my weapon. My brother has his sword, King Robert has his warhammer, and I have my mind… and a mind needs books as a sword needs a whetstone, if it is to keep its edge.” Tyrion tapped the leather cover of the book. “That’s why I read so much, Jon Snow.”