Duras, the other Klingon in the shot, is offended that Picard has the audacity to act in command. Picard says that he's not here to command, Duras then challenges him to a fight which he thinks he'll easily win because Starfleet doesn't train its officers in combat. Line. Episode is "Sins of the Father" S03E17.
Not command, but the audacity to act as Worf's personal advocate in front of the Klingon High Council during the trial of honor of Worf's family. Duras questions his qualifications, being "only" human. To which he responds with his many achievements and martial prowess before inviting him to test that anytime he wants. Just Picard being a general badass.