'clever snake, simple pigeon' - funny double translation

I'm sure it's from the Christian New Testament, Matthew 10:16, where Jesus says "... be as wise as serpents and as harmless as doves". Too bad the translators missed the reference; the original (or at least, the English version, if the Yu Aida didn't in fact take it from a Japanese translation of the Bible) has a better ring to it. 'simple' doesn't quite capture 'harmless', which indeed is the tone of the saying, in the episode.