Who said "Art thou a slave? Then thou canst not be my friend."?

This quote is attributed to Zarathustra.

Art thou a slave? Then thou canst not be my friend. - Zarathustra

"Art thou a slave? Then thou canst not be my friend."

Zarathustra Freedom

Character in Thus Spoke Zarathustra

"I teach you the Übermensch. Man is something that shall be overcome."

"One must have chaos within oneself to give birth to a dancing star."

"The snake that cannot shed its skin perishes."

"I love those who do not first look behind into the past before they look down at the abyss."

"Freedom to pursue your passion is precious."

"Freedom comes at a cost."

"Order isn't restriction. It's freedom."

"Freedom comes with responsibility"