Nicky: I feel like such an idiot.
Frank: Then remember that feeling and learn from it.

Nicky: I think you're taking this personally.
Frank: A flag just like that one draped your uncle's coffin. Yeah, it's personal.

"By general law, life and limb must be protected, yet often a limb must be amputated to save a life, but a life is never wisely given to save a limb," Abraham Lincoln. This department is the life, Officer Whitman is a limb.

Erin: How well do you still know him?
Frank: What's that suppose to mean?
Erin: It means. people can change. It means. what was hi jinx back in the day can become a hard core lifestyle later on. I mean, I've read his book, he is no altar boy.
Frank: Doesn't make him a felon.
Erin: Shooting up a strip club does.

Frank: Erin's taking a look.
Lenny: That's good.
Frank: I didn't ask her to over look, just look.

Erin: Do you believe him?
Frank: Yeah, I think I do.
Erin: That “think” kind of waters it down.

Baker: Something occurred to me today. You are the only member of this department to have presided over a line of duty death both as the commissioner and as a fallen officer's father.
Frank: Meaning?
Baker: That maybe you should hold off meeting with the mayor until...
Frank: Until I'm calm. That'll be never.

I would like you to put on an NYPD uniform, and 20 lbs. of equipment, and a gun belt, and run up six flights of stairs to save a woman who is being beaten by her boyfriend, and then, I would like you to be raked over the coals for your effort. And then, when you have that frame of reference, maybe we can talk.

Part of what we love most about the job is that there's always a fresh pain in the ass around the corner.

Kelly: It gets resolved the way most disputes do. Nobody gets everything they want.
Frank: Perps do. It's free money.
Kelly: It's nickels on the dollar.
Frank: They're still free nickels.

Gee, I must have missed the part that was underlined, italicized, and highlighted.

Of whom much is given, much is expected.