Luke 15:15-16

"So he went and hired to one of the citizens of that land, who sent him out into the fields to feed swine.

2 Peter 2:22

In their case it has happened according to the true proverb, The dog returns again to his own vomit, and The sow, after washing, to her wallowing in the mire.

Treasury of Scripture Knowledge

Summary

And the swine, because it divideth the hoof, yet cheweth not the cud, it is unclean unto you: ye shall not eat of their flesh, nor touch their dead carcase.

Bible References

The swine

Luke 15:15
"So he went and hired to one of the citizens of that land, who sent him out into the fields to feed swine.
2 Peter 2:22
In their case it has happened according to the true proverb, The dog returns again to his own vomit, and The sow, after washing, to her wallowing in the mire.