Plutarch, Theseus
Bernadotte Perrin, Ed.

As he went forward on his journey and came to the river Cephisus, he was met by men of the race of the Phytalidae, who greeted him first, and when he asked to be purified from bloodshed, cleansed him with the customary rites, made propitiatory sacrifices, and feasted him at their house. This was the first kindness which he met with on his journey.

It was, then, on the eighth day of the month Cronius, now called Hecatombaeon, that he is said to have arrived at Athens. And when he entered the city, he found public affairs full of confusion and dissension, and the private affairs of Aegeus and his household in a distressing condition. [2] For Medea, who had fled thither from Corinth, and promised by her sorceries to relieve Aegeus of his childlessness, was living with him. She learned about Theseus in advance, and since Aegeus was ignorant of him, and was well on in years and afraid of everything because of the faction in the city, she persuaded him to entertain Theseus as a stranger guest, and take him off by poison. Theseus, accordingly, on coming to the banquet, thought best not to tell in advance who he was, but wishing to give his father a clue to the discovery, when the meats were served, he drew his sword, as if minded to carve with this, and brought it to the notice of his father. [3] Aegeus speedily perceived it, dashed down the proffered cup of poison, and after questioning his son, embraced him, and formally recognized him before an assembly of the citizens, who received him gladly because of his manly valor. And it is said that as the cup fell, the poison was spilled where now is the enclosure in the Delphinium,¹ for that is where the house of Aegeus stood, and the Hermes to the east of the sanctuary is called the Hermes at Aegeus's gate.