No...it's not the opening line of a joke. It's an interesting anecdote I first heard in a class a few years ago and came across the actual source a couple of days ago. Thought I'd share.
Rabbi Yosef Ibn Aknin, a 12th-13th century thinker, wrote, among other things, a commentary on Song of Songs called "The Divulgence of Mysteries and the Appearance of Lights". The commentary included many references to Islamic philosophy and Arabic linguistics. At the end of the work, he dedicated a chapter to explaining why he used so much foreign (non-Jewish) material in his commentary. He defended this by bringing many examples of sages who consulted non-Jews to understand different aspects of Torah. One of the most interesting anecdotes he brought is about Rav Hai Gaon:
Rabbi Yosef Ibn Aknin, a 12th-13th century thinker, wrote, among other things, a commentary on Song of Songs called "The Divulgence of Mysteries and the Appearance of Lights". The commentary included many references to Islamic philosophy and Arabic linguistics. At the end of the work, he dedicated a chapter to explaining why he used so much foreign (non-Jewish) material in his commentary. He defended this by bringing many examples of sages who consulted non-Jews to understand different aspects of Torah. One of the most interesting anecdotes he brought is about Rav Hai Gaon:
"Rav Hai and his students had difficulty interpreting the verse "...let my head not refuse such choice oil..." (שמן ראש אל יני ראשי) (Tehillim 141:5). The people in the study hall debated the meaning, and Rabbeinu Hai z"l commanded Rabbi Matzliach to go to the Katolik (=high-ranking Christian priest) of the Christians and to ask him what he knew regarding the meaning of this verse. And this was not good in his (=Rabbi Matzliach's) eyes. And when he (=Rav Hai) z"l saw that this [task] was difficult in the eyes of Rabbi Matzliach, he rebuked him, stating "For the forefathers and ancient pietists will be a proof to us, [for they] would query regarding linguistics and interpretations from men of other religions." (Hebrew here)