The Iliad 24.287–298

Thereafter make thou prayer unto the son of Cronos, lord of the dark chouds, the god of Ida, that looketh down upon all the land of Troy, and ask of him a bird of omen, even the swift messenger that to himself is dearest of birds and is mightiest in strength; let him appear upon thy right hand, to the end that marking the sign with thine own eyes, thou mayest have trust therein, and go thy way to the ships of the Danaans of fleet steeds. But if so be Zeus whose voice is borne afar grant thee not his own messenger, then I of a surety should not urge thee on and bid thee go to the ships of the Argives, how eager soever thou be.