One Piece Chapter 1, page 47-49: Romance Dawn

Shanks floats in the quiet water, holding Luffy. He says gently: "Luffy, I'm sorry. Makino told me what happened. You stood up for me." Luffy begins to sob uncontrollably: "Shanks!!! B-but..." Shanks smiles warmly: "Hey, stop crying! You're a tough guy, remember?" Luffy looks up, crying hysterically: "WHAT ABOUT YOUR ARM!!?" Shanks' left arm has been completely bitten off, bleeding heavily into the sea.

Shanks smiles softly, comforting the crying boy: "It's a small price to pay... Just an arm... I'm just glad you're okay." Luffy buries his face in Shanks' shoulder and wails in grief. Narration boxes explain: "Luffy understood why Shanks wouldn't take him out to sea. The dangers of the sea were too great... And he was not yet strong enough... But most of all, Luffy realized what a great man Shanks was. He vowed to be just like him one day.

Sometime later, Shanks' pirate ship is fully loaded and preparing to set sail from the harbor. Shanks stands on the dock, talking to Luffy: "We've been using this harbor as a base of operations for a long time. Maybe too long. Are you sad?" Luffy smiles bravely: "Yeah, I'm sad... But I won't ask you to take me with you! I've decided to become a pirate on my own!" Shanks sticks his tongue out: "There's no way you can become a pirate! It wouldn't do you any good. You're still too little!" Luffy yells back: "Oh yes I will!!! One day I'll have a ship and crew better than yours!! And we'll have the biggest hoard of treasure in the world!!