Who said "A commander must be strong, but also just."?

This quote is attributed to Grey Worm.

A commander must be strong, but also just. - Grey Worm

"A commander must be strong, but also just."

Grey Worm Leadership

"I am Grey Worm. I have no name."

"Unsullied do not fear death."

"We are the dragons' soldiers."

"A soldier's duty is to obey."

"A leader must be fair and just."

"Integrity is everything."

"One must take responsibility for one's environment."

"In this house, I make the decisions"