In The Old Man and the Sea, Santiago is a teacher, mentor, and spiritual holy man for his disciple Manolin. Here are some lessons he teaches the boy:
Vocation: Santiago teaches the boy the right way to fish: out of love and respect for nature, not for money. Unlike the other fisherman, who are more concerned over volume, Santiago fishes for that singular great fish. As such, he is a fisher of men (one who seeks converts) as well. He is preparing Manolin to become a wise and dedicated fisherman, like himself.
Humility: Santiago is a shining example of modesty. Even though he has caught a great fish, perhaps the biggest marlin ever caught in these waters, he does not brag or announce it to the village upon his return. Granted, the flesh has been torn from the carcass, but Santiago is still an example of suffering and self-deprecation.
Persistence: Santiago has gone 84 straight days without catching a fish. Still, he approaches each day the same: with hope and respect. He does not curse God, nature, or his bad luck. Manolin would do well to maintain Santiago's even keel.
Respect: Whereas the other fishermen gossip and talk behind Santiago's back, insulting him, Santiago refrains from idle chatter about others not present. He gives his attention completely to teaching the boy, and his lessons are free from insult, sarcasm, and negativity. All are brothers, man and fish, to the old man.
Suffering: Upon his return, Santiago is a Christ-like emblem of suffering. He has brought only a worthless carcass home. He is tired and broken, but he is not defeated in spirit. He thereby achieves a victory over his suffering. Manolin knows that the old man will go back out to the same waters in the morning, undeterred by past struggle.
Courage: this is his greatest lesson. Even though he is old, a victim of bad luck, and near retirement, Santiago dares to go far out from land to dangerous shark-infested waters. No one else, not even the younger fishermen, would dare risk his life for such greatness.
in short words : the old man treats the boy as a peer not like a son nor a friend