Luke 15:15-16

And having gone he joined himself to one of the citizens of that country: and he sent him into his fields to feed swine:

2 Peter 2:22

It has happened unto them according to the old proverb, The dog having returned to his own vomit; and the sow that had washed to 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
And having gone he joined himself to one of the citizens of that country: and he sent him into his fields to feed swine:
2 Peter 2:22
It has happened unto them according to the old proverb, The dog having returned to his own vomit; and the sow that had washed to wallowing in the mire.