The proud trusts in himself; the just lives by his faith. It is the proud who are self-sufficient and who fail to realize the necessity of patient endurance and trust in God. In contrast to the proud, the just will be truly preserved through his faithfulness to God. Faith is not a one-time act, but a way of life. The true believer, declared righteous by God, will persevere in faith as the pattern of his life (Hebrews 3:12-14).
Commentary from the MacArthur study bible, notes for Habakkuk 2:4 and Hebrews 10:37, 38.