In today’s Western civilization, dogs are commonly seen as pets and so treated with love and care. In many other civilizations, including the Greco-Roman civilization into which Christ Jesus was sending his Revelation (Revelation 1:11), dogs were scavengers living alongside humans on whatever scraps they could find (Exodus 22:31; 1 Kings 14:11; Psalm 68:23). So references to dogs were habitually derogatory (Matthew 7:6; Philippians 3:2; 2 Peter 2:22). Applied to people, the term indicates the unclean and the unwanted, for they have not washed their robes. So they are still filthy
(Revelation 22:11).
15 Outside are the dogs and sorcerers and the sexually immoral and murderers and idolaters, and everyone who loves and practices falsehood.