Easton's Bible Dictionary (1897)/Dog

Dog : Frequently mentioned both in the Old and New Testaments. Dogs were used by the Hebrews as a watch for their houses (Isa. 56:10), and for guarding their flocks (Job 30:1). There were also then as now troops of semi-wild dogs that wandered about devouring dead bodies and the offal of the streets (1 Kings 14:11; 16:4; 21:19, 23; 22:38; Ps. 59:6, 14).

As the dog was an unclean animal, the terms "dog," "dog's head," "dead dog," were used as terms of reproach or of humiliation (1 Sam. 24:14; 2 Sam. 3:8; 9:8; 16:9). Paul calls false apostles "dogs" (Phil. 3:2). Those who are shut out of the kingdom of heaven are also so designated (Rev. 22:15). Persecutors are called "dogs" (Ps. 22:16). Hazael's words, "Thy servant which is but a dog" (2 Kings 8:13), are spoken in mock humility=impossible that one so contemptible as he should attain to such power.