Who said "The mind must be trained as rigorously as the body."?

This quote is attributed to Grey Worm.

The mind must be trained as rigorously as the body. - Grey Worm

"The mind must be trained as rigorously as the body."

Grey Worm Education

"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."

"Education opens doors."

"Education opens doors to endless possibilities."

"I ain't got the education you got, bub."

"You can't put a price on history."