The danger of so many outlines of biblical theology offered to us today is that they suggest that Old and New Testaments may be used indifferently to illustrate one and the same level of God’s dealing with man, and they assume that the language in which this dealing is expressed is essentially Hebrew even where it is accidentally Greek. These interpreters concede that it was not necessary for a Gentile convert to be circumcised, but they imply that he had to be Hebraized if he was to belong to the Christian church. It is high time that we are willing to look critically at this basic assumption in the light of the New Testament evidence. When the glorious vision on the way to Damascus halted Saul in his tracks, it was a Greek saying that reinforced the disclosure of the risen Christ. ‘It is hard to kick against the goads’ was something Greeks had long said to each other. Paul did not report this when explaining himself to rowdy Jews in the Hebrew tongue, but there is no reason to suppose that he (or Luke) invented it for his speech before Agrippa. – J.B. Skemp, The Greeks and the Gospel, 8
From footnote 11 on the same page:
Acts 26.14 (compare 9.5, where the Laudianus (sixth cent.) and Latin manuscripts include the words, but against the consensus; and 22.8). The saying pros kentra laktizeo occurs as early as Pindar’s second Pythian ode (at the end), and therefore before 470 B.C. With kulon teinein for laktizein but in the same sense it is found in the Prometheus Vinctus of Aeschylus at line 323; and the actual phrase is found in Aeschylus’ Agamemnon, 1633, and Euripides’ Bacchae, 793. It had evidently passed from Attic literature into the common language and thought of the near east.