Who said "Strength is not merely physical; it is will."?

This quote is attributed to Lannister.

Strength is not merely physical; it is will. - Lannister

"Strength is not merely physical; it is will."

Lannister Strength

"A Lannister always pays his debts."

"I am the god of tits and wine."

"You are an awful man."

"I drink and I know things."

"Strength comes from within."

"A woman should be proud of who she is."

"A strong woman can overcome anything."

"The only thing I'm good at is killing."