Antonyms for the phrase "swears to" include words like denies, refutes, declines, disavows, negates, and repudiates. These words essentially mean the opposite of what "swears to" conveys, which is a promise or oath to tell the truth. When someone denies or refutes something, it means they are rejecting or disagreeing with it, instead of making a commitment to it. Similarly, if someone declines or disavows something, they are refusing or disowning it, rather than giving their word. Finally, negating or repudiating something denotes a complete rejection or denial of a claim or statement.