The prophet requested that God answer his cry about violence and corruption in the land (vv. 1-4). God replied that He would bring in the Chaldeans to chastise Judah (vv. 5-11). But the prophet remonstrated that God was holy and he could not understand how God could use a nation more evil than Judah as His instrument of judgement.
"I will take my stand to watch...and look forth to see what he [God] will say to me," wrote Habakkuk (2:1). So the waiting prophet (v.1) was met by a willing Lord (vv. 2-5) who told him that while "the righteous live by faith," "he whose soul is not upright in him shall fail." Therefore, Habakkuk lamented the sins of his woeful nation (vv. 6-20), particularly the sins of those who rob the poor and spread violence throughout the land.
Habakkuk's faith was both tested and taught; his faith then gave triumphant expression first to the person of God who taught him (vv. 1-5): "His glory covered the heavens, and the earth was full of praise"; then to the power of God (vv. 6-12): "Thou didst bestride the earth in furry, thou didst trample the nations in anger"; and finally to the purpose of God (vv. 13-19): "Thou wentest forth for the salvation of thy people."
Norman Geisler, A Popular Survey of the Old Testament, p. 260-261