Who said "But first, you must prove yourself worthy."?

This quote is attributed to Palpatine.

But first, you must prove yourself worthy. - Palpatine

"But first, you must prove yourself worthy."

Palpatine Motivation

"Did you ever hear the tragedy of Darth Plagueis the Wise?"

"The dark side of the Force is a pathway to many abilities some consider to be unnatural."

"Have you ever heard of the tragedy of Darth Plagueis? I thought not."

"Unlimited power!"

"I believe in working hard for what you want."

"Never underestimate the power of determination."

"I don't need a reason to fight."

"The most important thing is the mission. Nothing else matters."