Zeus-Ammon visits Herakles in disguise

“The Thebans, and those who by the Theban example will not touch sheep, give the following reason for their ordinance: they say that Heracles wanted very much to see Zeus and that Zeus did not want to be seen by him, but that finally, when Heracles prayed, Zeus contrived to show himself displaying the head and wearing the fleece of a ram which he had flayed and beheaded. It is from this that the Egyptian images of Zeus have a ram’s head; and in this, the Egyptians are imitated by the Ammonians, who are colonists from Egypt and Ethiopia and speak a language compounded of the tongues of both countries. It was from this, I think, that the Ammonians got their name, too; for the Egyptians call Zeus “Amon”. The Thebans, then, consider rams sacred for this reason, and do not sacrifice them. But one day a year, at the festival of Zeus, they cut in pieces and flay a single ram and put the fleece on the image of Zeus, as in the story; then they bring an image of Heracles near it. Having done this, all that are at the temple mourn for the ram, and then bury it in a sacred coffin.” – Herodotus 2.42