Why does Theseus protect Oedipus at Colonus?

In Sophocles' play Oedipus at Colonus, Theseus, the noble king of Athens, grants Oedipus sanctuary when the aged, blind exile arrives at a sacred grove near the city.12

Theseus protects Oedipus primarily as an act of refuge and hospitality. By providing this shelter, Athens secures a profound spiritual benefit: it is prophesied that the resting place of Oedipus will become a source of defense and a benevolent power for the land that grants him sanctuary. Consequently, Theseus’s protection serves both as a moral duty to a suffering suppliant and as a strategic blessing for the future security of Athens.132