John Gill's Exposition of the Whole Bible
Isaiah 37:31
And the remnant that is escaped of the house of Judah,.... The few that escaped out of the cities of Judah, upon Sennacherib's invasion of the land, and besieging and taking the fenced cities thereof, who fled to Jerusalem for safety; these were a type of the remnant, according to the election of grace, the few that are chosen of God, the special people redeemed by Christ, the little flock of his, the small number that enter in at the strait gate, and are saved; and who escape, not the fall of Adam, nor the imputation of his sin, nor the corruption of nature, nor the pollutions of the world in a state of nature; but who escape the vengeance of divine justice, the curse of a righteous law, wrath to come, and the damnation of hell; which is owing to the love of God, the covenant of his grace, the suretyship engagements of Christ, and his performance of them; these are the household of faith, God's confessing and professing people, who are Jews inwardly, of whom there are but a few; of these it is said, they
shall again take root downward, and bear fruit upward. The Targum is,
"as a tree which sends forth its roots below, and lifts up its branches above.''
The sense is, that those people that fled from their own habitations to Jerusalem should return thither again upon the breaking up of the siege, and be firmly settled, and live peaceably and prosperously, abounding with all good things, which may be applied, mystically, to true believers taking root again in the love of God, which is a hidden root, and is the source of salvation, and all the blessings of it, and is in itself immovable; and though the saints are secured in it, and by it, and nothing can root them out of it, yet they are sometimes shaken with doubts and fears about their interest in it; when there is again a fresh taking root in it, and that is, when they have a strong and lively persuasion of it, which produces fruitfulness in the exercise of faith, hope, and love, and in Gospel obedience; and also to their taking root in Christ, who is as a root unto them, hidden, and out of sight to the world, mean and abject, yet the source of all happiness to the saints, who have a being in him, are born by him, and receive sap and nourishment from him; and though their faith of interest in him may be sometimes shaken, yet there is a fresh taking root by new acts of faith upon him, which produce fruitfulness; the fruits brought forth by such are good works, which spring from the seed of grace, are owing to divine goodness, to the dews of grace, are pleasant and acceptable to God through Christ, and profitable unto men; these are called the fruits of the Spirit, and of righteousness, and are meet for repentance, and are brought forth openly and publicly, which may be signified by being bore upwards.