Matthew 7:6
"Give not that which is holy to the dogs, nor throw your pearls to the swine; otherwise they will trample them under their feet and then turn and attack you.
Philippians 3:2
Beware of 'the dogs,' the bad workmen, the self-mutilators.
2 Peter 2:22
Their case is that described in the true proverb, "A dog returns to what he has vomited," and also in the other proverb, "The sow has washed itself and now goes back to roll in its filth."
Revelation 22:15
The unclean are shut out, and so are all who practise magic, all fornicators, all murderers, and those who worship idols, and every one who loves falsehood and tells lies.