What ultimately led the old servant to give the baby to the Messenger?

The old servant ultimately gave the baby to the Messenger out of pity for the child. This decision stems from the servant's compassion upon witnessing the plight of the infant, who was destined to be abandoned due to the dire circumstances surrounding its birth. The servant's empathetic nature facilitated a significant turning point in the story, as he hoped to spare the child from a fate of exposure and death by offering it a chance at life through the Messenger.

This act of kindness is crucial to the plot, as it sets off a chain of events that leads to Oedipus's eventual discovery of his true origins, highlighting themes of fate and the intersection of personal choices with predetermined destiny. By caring for the baby, the servant's actions counteract the prophecy's dark foretelling, even if he is unaware of the profound implications his decision will later have on Oedipus's life.