I believe it is significant when an Old Testament verse is quoted in the New Testament. When the verse is quoted twice, that is a big deal. But when a verse is quoted three times, with each instance in a different letter, there is a spiritual principle being taught that has a wider application. Habakkuk 2:4 is just such a verse.
But the just shall live by his faith. (Habakkuk 2:4b NKJV)
How appropriate that this little verse is quoted in Romans, Galatians, and Hebrews.

The Just:
For I am not ashamed of the gospel of Christ, for it is the power of God to salvation for everyone who believes, for the Jew first and also for the Greek. For in it the righteousness of God is revealed from faith to faith; as it is written, The just shall live by faith. (Romans 1:16, 17 NKJV)
If I had to sum up the message I’d Paul’s letter to the church in Rome in just one word, that word would be justification. For it is in Romans that we are shown when, where, and how justification by faith happens. The “how” is by faith, as the previous verse says. The where is in our hearts (Romans 5:1-5), and the “when” is at obedience in baptism (Romans 6:3-10).

Shall Live:
But that no one is justified by the law in the sight of God is evident, for the just shall live by faith. (Galatians 3:11 NKJV)

In Galatians we have been provided with practical instruction for Christian living. But are also told that “I have been crucified with Christ; it is no longer I who live, but Christ lives in me; and the life which I now live in the flesh I live by faith in the Son of God, who loved me and gave Himself for me.” (Galatians 2:20 NKJV)
I cannot help but see an implied reference to baptism here as well.

By Faith:
Now the just shall live by faith; But if anyone draws back, My soul has no pleasure in him. (Hebrews 10:38 NKJV)
There is an entire chapter in Hebrews talking about faith. We also see that without faith, it is impossible to please God. Feeding our faith is the key to not drawing back. Faith in God is the very source of our spiritual life, and if we quit on God, we are left with less than nothing. In fact, it would be better to have never begun with God.
“For it would have been better for them not to have known the way of righteousness, than having known it, to turn from the holy commandment delivered to them.” (2 Peter 2:21 NKJV)
In reality, in the vast majority of cases, salvation is not lost — it is left.

Do you want to be justified and have eternal life?then have faith in God. But how do we get faith? “So then faith comes by hearing, and hearing by the word of God.” (Romans 10:17 NKJV) Get into the Word of God and feed your faith. And once you are in Christ via obedience in baptism, continue to stay in the Word and let your mind be transformed.