Now the just shall live by faith - This is a part of the quotation from Habakkuk Habakkuk 2:3-4, which was probably commenced in the previous verse; see the passage fully explained in the notes on Romans 1:17. The meaning in the connection in which it stands here, in accordance with the sense in which it was used by Habakkuk, is, that the righteous should live by “continued confidence” in God. They should pass their lives not in doubt, and fear, and trembling apprehension, but in the exercise of a calm trust in God. In this sense it accords with the scope of what the apostle is here saying. He is exhorting the Christians whom he addressed, to perseverance in their religion even in the midst of many persecutions. To encourage this he says, that it was a great principle that the just, that is, all the pious, ought to live in the constant exercise of “faith in God.” They should not confide in their own merits, works, or strength. They should exercise constant reliance on their Maker, and he would keep them even unto eternal life. The sense is, that a persevering confidence or belief in the Lord will preserve us amidst all the trials and calamities to which we are exposed.
But if any man draw back, my soul shall have no pleasure in him - This also is a quotation from Habakkuk 2:4, but from the Septuagint, not from the Hebrew. “Why” the authors of the Septuagint thus translated the passage, it is impossible now to say. The Hebrew is rendered in the common version, “Behold, his soul which is lifted up is not upright in him;” or more literally, “Behold the scornful; his mind shall not be happy” (Stuart); or as Gesenius renders it, “See, he whose soul is unbelieving shall, on this account, be unhappy.” The sentiment there is, that the scorner or unbeliever in that day would be unhappy, or would not prosper - לה ישרה lo’ yaasharaah. The apostle has retained the general sense of the passage, and the idea which he expresses is, that the unbeliever, or he who renounces his religion, will incur the divine displeasure. He will be a man exposed to the divine wrath; a man on whom God cannot look but with disapprobation. By this solemn consideration, therefore, the apostle urges on them the importance of perseverance, and the guilt and danger of apostasy from the Christian faith. If such a case should occur, no matter what might have been the former condition, and no matter what love or zeal might have been evinced, yet such an apostasy would expose the individual to the certain wrath of God. His former love could not save him, any more than the former obedience of the angels saved them from the horrors of eternal chains and darkness, or than the holiness in which Adam was created saved him and his posterity from the calamities which his apostasy incurred.