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

This quote is attributed to Sif.

The mind must be trained like the body. - Sif

"The mind must be trained like the body."

Sif Education

"I have waited lifetimes for this moment."

"A warrior's heart beats strongest in battle."

"We are bound by more than just duty."

"The past shapes who we become."

"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."