C185 Celestial Dragon People Incident

The search for Rayleigh began with ease, as Luffy and his crew quickly located him at the human auction house, where he was about to sell himself. Upon seeing Luffy's straw hat, Rayleigh revealed that he had long been looking forward to meeting him.

That straw hat had once belonged to Roger, then passed on to Red Hair Shanks, who in turn gave it to Luffy, symbolizing a legacy