Do not give a beautiful or precious thing to a person who is totally unable to appreciate its value. The proverb is very often used by those who consider themselves superior beings, more intelligent or gifted than their fellows.
‘I read some of my poetry aloud to them, but it was casting pearls before swine. They obviously didn’t understand a word of it and soon started yawning, looking at their watches and fidgeting in their chairs.’
The source of the proverb is Matthew, vii, 6:
‘Give not that which is holy unto the dogs, neither cast ye your pearls before swine, lest they trample them under their feed, and turn again and rend you.’