Who said "The Red Viper strikes when least expected."?

This quote is attributed to Oberyn Martell.

The Red Viper strikes when least expected. - Oberyn Martell

"The Red Viper strikes when least expected."

Oberyn Martell

"I am the viper. When the time comes, I will strike."

"Elia of Dorne. My sister. You raped her. You murdered her children."

"I want to look the man in the eye and see the fear in his heart."

"The man who passes the sentence should swing the sword."