He makes this suggestion during a council of Trojan elders in Book 3 of Homer's *The Iliad*. Antenor argues that returning Helen would end the war and prevent further bloodshed. He points out that the war was started because of Helen's abduction, and that returning her would be the most logical and peaceful solution.
However, his suggestion is ultimately rejected by the other Trojan elders, who are motivated by pride and a desire to win the war.