In my last post, I talked about how Habakkuk struggled with difficult questions and waited on the Lord for answer. We’ll see that God’s answer might not be quite what we’d expect.
Habakkuk 2:4 reads, “Behold, his soul is puffed up; it is not upright within him, but the righteous shall live by his faith.”
Those who perpetrated injustices (in this case the Babylonians) were filled with pride, but in a marked contrast the righteous lived by faithfulness.
Commentator Cyril Barber put it this way, “Faith in God was the key to consistent living, even though violence abounded and justice was perverted (1:2–4). That short statement helps believers to persevere even though God chastens them (1:5–11) and they cannot understand his ways (1:12–17). It provides a solution to the doubt they sometimes feel in His all-wise providence (2:1–3), and helps them to understand his righteous judgments (2:4–20). In the final analysis, faith provides the key to understanding the Lord’s sovereign purpose, and it leads men to worship (3:1–19).” 
Rather than explain why terrible things happened, the Lord begin with telling Habakkuk how he was to live his life in the midst of these awful things. Faithfulness becomes paramount when surrounded by a sea of injustice.
The phrase “the righteous (or just) shall live by faith” becomes a key phrase in the New Testament building off the first occurrence here in Habakkuk.
The apostle Paul quoted it twice (Rom. 1:16–17 and Gal. 3:11) in a spiritual sense to show the crucial point of salvation through faith.
As commentator Kenneth Barker says, “He took God’s message to Habakkuk to its final emphasis: those who are judged righteous as a result of their faith shall live.”
The author of Hebrews quotes this verse when talking about the perseverance of believers under hardship (10:37–38). Notably, these verses help introduce what has commonly come to be called “the faith chapter” (ch. 11).
As a faithful servant and seeker of God, Habakkuk fits right in with the long list of faithful heroes.
 Cyril J. Barber, Habakkuk & Zephaniah—Everyman’s Bible Commentary (Chicago: Moody Publishers, 1985), 39.
 Kenneth L. Barker, Micah, Nahum, Habakkuk, Zephaniah, vol. 20, The New American Commentary (Nashville: Broadman & Holman Publishers, 1999), 326.