Who said "A worthy adversary is often a worthy teacher."?

This quote is attributed to Hadrian.

A worthy adversary is often a worthy teacher. - Hadrian

"A worthy adversary is often a worthy teacher."

Hadrian Wisdom

Emperor Ancient Rome 76–138

"Nothing is harder to bear than a good example."

"I have always strived to be the best, but I have also learned that the best is not always perfection."

"A man who fears nothing is more dangerous than a man who fears something."

"The greatest luxury is knowledge."

"I'm not angry, I'm just disappointed."

"The best things in life are free."

"You can't have everything in life, but you can have what matters most."

"A woman's intuition is rarely wrong."