Matthew 7:6 - Give not that which is holy unto the dogs, neither cast ye your pearls before swine, lest they trample them under their feet, and turn again and rend you.
Nice, you'd think Jesus should've followed his own advice, eh. He did know the consequences didn't he. Since today we're big on context, the preceding verse is about hypocrisy, which ties rather nicely with the predominant perception about christians.