The Doctor: But sleep is vital. Sleep is wonderful. Even I sleep.
Clara: When?
The Doctor: Well, when you're not looking.

24 hours ago this station fell silent. No comm signal, nothing. Dead. We've come to find out why.

Nagata

You can't fight them Doctor. There's no point. They're the future. A new life form. A better life form. It's very clear to me now, they made me understand. And we're to be their food.

Rassmussen

Nagata: What are you doing?
The Doctor: I've hacked into your helmet-cams.
Nagata: What?
The Doctor: Reviewing the footage. There's something not right here.
Nagata: We don't have helmet-cams.

They came to find me. This is my station. My lab. I've pieced together the rescue as best I could.

Rassmussen

Osgood: Never really met Clara. Pretty strong, yeah?
The Doctor: She was amazing.
Osgood: No, not was... is. It's not from the Zygon. It's from Clara.
The Doctor: How?
Osgood: She's not dead. She's in a pod somewhere.

The Doctor: Let me negotiate peace. You can't commit mass murder...
Kate: Then why did you leave the gas with us?
The Doctor: The boxes are safeguards for both species.

Bonnie: It's empty, isn't it? Both boxes. There's nothing in them, just buttons.
The Doctor: Of course, and you know how you know that? Because you've started to think like me.

You know, I'm over two thousand years old. I'm old enough to be your messiah.

The Doctor

The only way anyone can live in peace, is if they're prepared to forgive.

The Doctor

The Doctor: I need to know. Which one are you?
Osgood 1: I'm Osgood.
The Doctor: Human or Zygon?
Osgood 1: I'll answer that question one day. And do you know when that day will be?
Osgood 2: The day nobody cares about the answer.

Clara: You must have thought I was dead for a while?
The Doctor: Yeah.
Clara: How was that?
The Doctor: Longest month of my life.
Clara: It could only have been 5 minutes.
The Doctor: I'll be the judge of time.

Doctor Who Season 9 Quotes

What have we got? What do we know? It's not an attack. It's not an invasion because, well that doesn't come with a fair warning. So, somebody needs our attention. Somebody who needs to put a gun to our heads to make us listen.

Clara

The Doctor: Tell me the name of the boy who isn't going to die today.
Boy: Davros. My name is Davros.