In both the OT and NT, dogs are never pets but regarded disdainfully as very unclean animals. The reasons for this are several:
- Dogs were unclean animals according to Torah regulations
- Dogs were scavengers (or at least allowed to be such)
- Untamed dogs are vicious and dangerous
- Dogs were almost never used in agrarian Israel and so they had no utility
- Cultural - dogs had a bad reputation in Israel
Therefore, one of the standard insults was to compare someone to a dog such as: Job 30:1, 2 Kings 9:10, 1 Kings 16:4, 21:24, 22:38, 14:11, Isa 56:11, Ps 68:23, 22:16, 59:6, 14, etc, etc.
In all these cases, the dog is used as a metaphor of something very low, disgusting and repulsive. (How times have changed!)
Therefore, when Abner used the metaphor of [dead] "dog's head" (2 Sam 3:8), he was accusing Ish-bosheth of lacking any civility toward him as his previous supporter. The Cambridge Commentary succinctly observes:
- Am I a dog’s head, &c.] Render, Am I a dog’s head belonging to Judah? This day do I shew kindness … and thou hast charged me! &c.
i.e. Am I at once despicable and hostile to your interests? Nay, I am
faithful to the house of Saul, otherwise I should long ago have made
terms with David by surrendering you into his hands.
In the East in ancient times as at the present day, dogs, although
used for guarding flocks and houses (Job 30:1; Isaiah 56:10), were
chiefly seen prowling about towns in a half-wild condition, owning no
master, living on offal and garbage. Cp. Psalm 59:14-15; 1 Kings
21:19; 1 Kings 21:23-24; 1 Kings 22:38. Hence the aversion with which
they were regarded, and “dog” became (1), as here, a term of reproach
and contempt; cp. 1 Samuel 17:43; 1 Samuel 24:14; 2 Samuel 9:8; 2
Samuel 16:9; 2 Kings 8:13 : (2) an expression for fierce and cruel men
(Psalm 22:16): (3) a name for impure persons (Matthew 7:6; Php 3:2;
Revelation 22:15). See Tristram’s Nat. Hist. of the Bible, p. 78.