One Piece Chapter 7, page 4: Chapter 7: Friends

Luffy cheerfully announces, "WE'RE HEADED FOR THE GRAND LINE!" Koby is completely shocked, screaming, "HUH!? THAT'S SUICIDE!!! THERE ARE ONLY TWO OF YOU! IF YOU GO THERE, YOU'LL JUST BE SAILING TO YOUR DEATHS! THE MOST BLOODTHIRSTY PIRATES IN THE WORLD ARE THERE!!!" Luffy looks unbothered. Zoro grins and says, "WELL, I GUESS IF WE'RE AFTER THE 'ONE PIECE'......THE GRAND LINE IS WHERE WE HAVE TO GO." Koby turns to Zoro in disbelief, crying, "ZOLO!? YOU AGREE WITH HIM!?" Luffy tells Koby, "WHAT'S IT TO YOU? YOU'RE NOT COMING WITH US."