'This song' is to be interpreted as a song, not with the cold-blooded accuracy proper to a scientific treatise. The logic of emotion is as sound as that of cool intellect, but it has its own laws and links of connection. First, the song sets in sharp contrast the two cities, describing, in verses 1-4, the city of God, its strength defences, conditions of citizenship, and the peace which reigns within its walls; and in verses 5 and 6 the fall and utter ruin of the robber city, its antagonist Jerusalem, on its rocky peninsula, supplies the form of Isaiah's thought; but it is only a symbol of the true city of God, the stable, invisible, but most real, polity and order of things to which men, even while wandering lonely and pilgrims, do come, if they will. It is possible even here and now to have our citizenship in the heavens, and to feel that we belong to a great community beyond the sea of time, though our feet have never trodden its golden pavements, nor our eyes seen its happy glories.
In one aspect, it is ideal, but in truth it is more real than the intrusive and false things of this fleeting present, which call themselves realities. 'The things which are' are the things above. The things here are but shows and shadows.
The city's walls are salvation. There is no need to name the architect of these fortifications. One hand only can pile their strength. God appoints salvation in lieu of all visible defences. Whom He purposes to save are saved. Whom He wills to keep safe are kept safe. They who can shelter behind that strong defence need no other. Weak, sense-governed hearts may crave something more palpable, but they do not really need it. A parapet on an Alpine road gives no real security, but only satisfies imagination. The sky needs no pillars to hold it up.
Then an unknown voice breaks in upon the song, calling on unnamed attendants to fling wide the gates. The city is conceived of as empty; its destined inhabitants must have certain qualifications. They must be righteous, and must 'keep faithfulness' being true to the God who is 'faithful and true' in all His relations. None but the righteous can dwell in conscious citizenship with the Unseen while here, and none but the righteous can enter through the gates into the city. That requirement is founded in the very nature of the case, and is as emphatically proclaimed by the gospel as by the prophet. But the gospel tells more articulately than he was enlightened to do, how righteousness is to be won. The last vision of the Apocalypse, which is so like this song in its central idea, tells us of the fall of Babylon, of the descent to earth of the New Jerusalem, and leaves as its last message the great saying, 'Blessed are they that wash their robes that they may ... enter in through the gate into the city.'
Our song gives some hint of similar thoughts by passing from the description of the qualifications for entrance to the celebration of the security which comes from trust. The safety which is realised within the walls of the strong city is akin to the 'perfect peace' in which he who trusts is kept; and the juxtaposition of the two representations is equivalent to the teaching that trust, which is precisely the same as the New Testament faith, is the condition of entrance. We know that faith makes righteous, because it opens the heart to receive God's gift of righteousness; but that effect of faith is implied rather than stated here, where security and peace are the main ideas. As some fugitives from the storm of war sit in security behind the battlements of a fortress, and scarcely hear the din of conflict in the open field below, the heart, which has taken refuge by trust in God, is kept in peace so deep that it passes description, and the singer is fain to give a notion of its completeness by calling it 'peace, peace.' The mind which trusts is steadied thereby, as light things lashed to a firm stay are kept steadfast, however the ship toss. The only way to get and keep fixedness of temper and spirit amid change and earthquake is to hold on to God, and then we may be stable with stability derived from the foundations of His throne to which we cling.
Therefore the song breaks into triumphant fervour of summons to all who hear it, to 'trust in Jab Jehovah for ever,' Such settled, perpetual trust is the only attitude corresponding to His mighty name, and to the realities found in His character. He is the 'Bock of Ages' the grand figure which Moses learned beneath the cliffs of Sinai and wove into his last song, and which tells us of the unchanging strength that makes a sure hiding-place for all generations, and the ample space which will hold all the souls of men, and be for a shadow from the heat, a covert from the tempest, a shelter from the foe, and a home for the homeless, with many a springing fountain in its clefts.
The great act of judgment which the song celebrates is now (vs.5, 6) brought into contrast with the blessed picture of the city, and by the introductory 'for' is stated as the reason for eternal trust. The language, as it were, leaps and dances in jubilation, heaping together brief emotional and synonymous clauses. So low is the once proud city brought, that the feet of the poor tread it down. These 'poor' and 'needy' are the true Israel, the suffering saints, who had known how cruel the sway of the fallen robber city was; and now they march across its site; and its broken columns and ruined palaces strew the ground below their feet. 'The righteous nation' of the one picture are 'the poor and needy' of the other. No doubt the prophecy has had partial accomplishments more than once or twice, when the oppressed church has triumphed, and some hoary iniquity been levelled at a blow, or toppled over by slow decay. But the complete accomplishment is yet future, and not to be realised till that last act, when all antagonism shall be ended, and the net result of the weary history of the world be found to be just these two pictures of Isaiah's -- the strong city of God with its happy inhabitants, and the everlasting desolations of the fallen city of confusion.
The triumphant hurry of the song pauses for a moment to gaze upon the crash, and in verse 7 gathers its lessons into a kind of proverbial saying, which is perhaps best translated 'The path of the just is smooth (or "plain"); Thou levellest smooth the path of the just.' To render 'upright' instead of 'smooth' seems to make the statement almost an identical proposition, and is tame. What is meant is, that, in the light of the end, the path which often seemed rough is vindicated. The judgment has showed that the righteous man's course had no unnecessary difficulties. The goal explains the road. The good man's path is smooth, not because of its own nature, but because God makes it so. We are to look for the clearing of our road, not to ourselves, nor to circumstances, but to Him; and even when it is engineered through rocks and roughnesses, to believe that He will make the rough places plain, or give us shoes of iron and brass to encounter them. Trust that when the journey is over the road will be explained, and that this reflection, which breaks the current of the swift song of the prophet, will be the abiding, happy conviction of heaven.
Lastly, the song looks back and tells how the poor and needy, in whose name the prophet speaks, had filled the dreary past, while the tyranny of the fallen city lasted, with yearning for the judgment which has now come at last. Verses 8 and 9 breathe the very spirit of patient longing and meek hope. There is a certain tone of triumph in that 'Yea,' as if the singer would point to the great judgment now accomplished, as vindicating the long, weary hours of hope deferred. That for which 'the poor and needy' wait is the coming 'in the path of Thy judgments.' The attitude of expectance is as much the duty and support of Christians as of Israel. We have a greater future clearer before us than they had. The world needs God's coming in judgment more than ever; and it says little for either the love to God or the benevolence towards man of average Christians, that they should know so little of that yearning of soul which breathes through so much of the Old Testament. For the glory of God and the good of men, we should have the desire of our souls turned to His manifestation of Himself in His righteous judgments. It was no personal end which bred the prophet's yearning. True, the 'night' round him was dreary enough, and sorrow lay black on his people and himself; but it was God's 'name' and 'memorial' that was uppermost in his desires. That is to say, the chief object of the devout soul's longings should be the glory of God's revealed character. And the deepest reason for wishing that He would flash forth from His hiding-place in judgments, is because such an apocalypse is the only way by which wilfully blind eyes can be made to see, and wilfully unrighteous hearts can be made to practise righteousness.
Isaiah believed in the wholesome effect of terror. His confidence in the power of judgments to teach the obstinate corresponds to the Old Testament point of view, and contains a truth for all points of view; but it is not the whole truth. We know only too well that sorrows and judgments do not work infallibly, and that men 'being often reproved, harden their necks.' We know, too, more clearly than any prophet of old could know, that the last arrow in God's quiver is not some unheard-of awfulness of judgment, but an unspeakable gift of love, and that if that 'favour shown to the wicked' in the life and death of God's Son does not lead him to 'learn righteousness,' nothing else will.
But while this is true, the prophet's aspirations are founded on the facts of human nature too, and judgments do sometimes startle those whom kindness had failed to touch. It is an awful thought that human nature may so steel itself against the whole armoury of divine weapons as that favour and severity are equally blunted, and the heart remains unpierced by either. It is an awful thought that there may be induced such truculent obstinacy of love of evil that, even when in 'a land of uprightness,' a man shall choose evil, and forcibly shut his eyes, that he may not see the majesty of the Lord, which he does not wish to see because it condemns his choice, and threatens to burn up him and his work together. A blasted tree when all the woods are green, a fleece dry when all around is rejoicing in the dew, a window dark when the whole city is illuminated, one black sheep amid the white flock, or anything else anomalous and alone in its evil, is less tragic than the sight, so common, of a man so sold to sin that the presence of good only makes him angry and restless. It is possible to dwell amidst the full light of Christian truth, and in a society moulded by its precepts, and to be unblessed, unsoftened thereby. If not softened, then hardened; and the wicked who in the land of uprightness deals wrongfully is all the worse for the light which he hated because it showed him the sinfulness of the sin which he obstinately loved and would keep.