Homer and Hesiod have attributed to the gods everything which is a shame and reproach among men, stealing, committing adultery, and deceiving each other.
Attributed to Xenophanes by Sextus Empiricus (Adversos Mathematicos, 9:193). Translation from S. F. Kirk, R. E. Raven and M. Schofield, The Presocratic Philosophers (2nd ed.; Cambridge: Cambridge University Press, 1984), 168.
If the attribution is correct, this is likely the oldest reference to Homer. It appears that the earliest direct quotations from the Iliad and/or the Odyssey are in Herodotus, 2:116 (Iliad 6:289-92, Odyssey 4:227-230, 235). If anyone knows of anything earlier, I’d sure like to know about it. I’m also looking for the earliest reference to or quotation from Iliad 12:200-209. If you are wondering why I filed this under Akkadian, I did because the project that drives me to raise this question deals with Akkadian texts.