There are no specific vows a Knight makes to a Sorceress. Seifer merely agrees with Edea/Ultimecia when she proposes he "leave his childhood behind" and Squall informally makes a promise to Rinoa to "be [her] knight." There is music that plays when Squall both gives his speech to Garden to bolster morale as well as when he rescues Rinoa from the Sorceress' Memorial that's entitled "The Oath" but it is nonlyrical.