The duel on Kwannot was a duel between Qui-Gon Jinn and his Padawan Obi-Wan Kenobi against the assassin Aurra Sing who had killed the Jedi Knight Mana Veridi. Both master and apprentice faced off against the assassin who gained the upper hand during their confrontation. But Sing fled and stole Veridi's lightsaber when she realized that the two Jedi were more than she had anticipated.
Kenobi later recalled this incident in 0 BBY to the smuggler Han Solo onboard the Millennium Falcon en route to Alderaan. Kenobi told Solo he liked to believe that Sing fled because she believed that Jinn and Kenobi were too powerful for her though that was just conjecture.