Concerning dogs: In Philippians 3:2, Paul told the Christians living in that Roman outpost to be wary of the dogs (βλέπετε τοὺς κύνας), that is, "those who mutilate the flesh" (or those who practice circumcision for the purpose of salvation). His words reflect the Jewish view of dogs (particularly scavenger dogs).
Also, in Rev. 22:15, "dogs" (οἱ κύνες) are debarred from the heavenly city of New Jerusalem. They are left outside of the gates along with those who practice spiritism and fornication, as well as idolators and liars and murderers. Bible commentator David Aune has a very informative section in his Revelation commentary. He notes that the MT (Masoretic Text) has the term KELEB for dog (Cf. Deut. 23:18 which has כֶּ֗לֶב).
Aune writes that κύων (dog) is ambivalent in Greco-Jewish literature, even though a number of pejorative references appear vis-a'-vis dogs. For while dogs were "economically beneficial" as "watch dogs and herding dogs," and while they were not necessarily considered unclean in halachic traditions--the term is clearly used pejoratively in 1 Sam. 17:43; 24:14; 2 Kings 8:13; Isa. 56:10-11; Matthew 7:6; 2 Pet. 2:22; Didache 9:5; Ignatius, Eph. 7:1.
Norman Hillyer (in his commentary on 2 Peter) likewise observes that κύων in 2 Pet. 2:22 denotes: "the wild scavenger of the streets and rubbish tips, not a pet house-dog" (208).