Hard to Find (2)
Dullabha Sutta  (AN 5:60)

“Monks, these five qualities are hard to find in one who has gone forth when old. Which five? It is hard to find one who has gone forth when old who is easy to instruct, hard to find one who grasps well what he has learned, hard to find one who learns with deference, hard to find one who can teach the Dhamma, hard to find one who has mastered the Vinaya.”

See also: DN 16