One Piece Chapter 5, page 15-17: CHAPTER 5: THE KING OF THE PIRATES AND THE MASTER SWORDSMAN

The flashback ends, returning to the present courtyard. Zoro, facing the firing squad, thinks, "I CAN'T DIE YET!! I PROMISED HER!" Captain Morgan commands, "FIRE!!!" Just as the Marines are about to shoot, Luffy launches himself out of the base window using his rubber powers, shouting, "GUM-GUM... ROCKET!!!" and crashes down into the courtyard.

Luffy lands directly in front of Zoro and Koby, stretching his body wide to block the incoming volley of bullets. The bullets hit his rubber chest with a rapid "BAP BAP AP PAP!" Zoro, Koby, Captain Morgan, and the Marines are completely dumbfounded, crying out, "YOU!?", "LUFFY!!!", and "STRAW HAT..." in utter disbelief.

Luffy's rubber body stretches backward under the impact of the bullets, and he proudly yells, "BULLETS CAN'T HURT ME!!" With a powerful snap, his body bounces the bullets right back at the execution squad. The Marines scream, "LOOK OUT!!!" as the bullets fly back, knocking them off their feet. Luffy bursts into loud laughter: "HA HA HA HA HA!!!