The Histories · 2.42

Now all who have a temple set up to the Theban Zeus or who are of the district of Thebes, these, I say, all sacrifice goats and abstain from sheep: for not all the Egyptians equally reverence the same gods, except only Isis and Osiris (who they say is Dionysos), these they all reverence alike: but they who have a temple of Mendes or belong to the Mendesian district, these abstain from goats and sacrifice sheep. Now the men of Thebes and those who after their example abstain from sheep, say that this custom was established among them for the cause which follows:—Heracles (they say) had an earnest desire to see Zeus, and Zeus did not desire to be seen of him; and at last when Heracles was urgent in entreaty Zeus contrived this device, that is to say, he flayed a ram and held in front of him the head of the ram which he had cut off, and he put on over him the fleece and then showed himself…

Herodotus of Halicarnassus · trans. G. C. Macaulay, 1890
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