Do not give what is holy to dogs or throw your pearls to swine.
“Do not give what is holy to dogs, or throw your pearls before swine, lest they trample them underfoot, and turn and tear you to pieces.” Matthew 7:6
This is reminiscent of several verses in the book of Proverbs, including the one about not arguing with a fool. It is not good stewardship of our time, energy, or influence. This leads to the converse principle of focusing our efforts on those who are faithful. This is not only for the sake of the faithful but also for the sake of the unfaithful. Scripture clearly teaches that those who are given much have more expected of them. Hence, we are only increasing judgement on those who are not faithful when we give them truth or guidance.