The language of this verse is clearly based on the Messianic prophecy of Isa. 9:2. Light has ever been a symbol of the divine presence (DA 464), of Him who dwells “in the light which no man can approach unto” (1 Tim. 6:16; see on Gen. 3:24; Luke 1:78). Jesus said, “I am the light of the world: he that followeth me shall not walk in darkness, but shall have the light of life” (John 8:12; see ch. 12:36). Our Saviour is “the true Light, which lighteth every man that cometh into the world” (John 1:9). Matthew applies the words of Isa. 9:1, 2 to Christ (ch. 4:14-16). The joy of salvation belongs to those who “walk in the light” (1 John 1:7), for their path is then “as the shining light, that shineth more and more unto the perfect day” (Prov. 4:18). See on John 1:4-9.

 Those who figuratively sit in darkness evidently do so because they cannot see where to walk. They need the “light” to guide their feet “into the way of peace.” Men sat, as it were, unsolaced, with longing eyes looking for the coming of the Light of life, whose coming would dispel the darkness and make plain the mystery of the future (see DA 32). For 4,000 years earth‘s skies had been dark with the ominous clouds of sin and death, and now for centuries no prophetic star had appeared through the gloom to guide the wayfarers of earth across the deserts of time in their search for the Prince of Peace (see DA 31). We too will find ourselves sitting unsolaced, with life empty and incomplete, unless the Day-star arises in our hearts and sheds abroad within our lives the light of eternal day (see 2 Peter 1:19).

 See on Ps. 23:4. The sentence of death is imposed upon all men as a result of sin (see Rom. 6:23). But “as in Adam all die, even so in Christ shall all be made alive” (1 Cor. 15:22). “The redeemed of the Lord ..., whom he hath redeemed from the hand of the enemy,” “wandered in the wilderness in a solitary way” and sat “in darkness and in the shadow of death” until the Saviour “brought them out of darkness and the shadow of death” and “led them forth by the right way” (Ps. 107:2, 4, 10, 14, 7).

Zacharias included himself with those whose feet the Messiah would “guide ... into the way of peace.”

 That is, the way of salvation, the way by which those whom sin has made enemies of God may once more be at peace with Him (Rom. 5:1, 10; 2 Cor. 5:18; Eph. 2:16). Christ, the Prince of Peace, accomplished this by making “reconciliation for the sins of the people” (Heb. 2:17). “God was in Christ, reconciling the world unto himself” (2 Cor. 5:19). “Great peace have they which love thy law” (Ps. 119:165). Christ came that He might give peace to us such as the world knows not and cannot offer (John 14:27). This “peace of God, which passeth all understanding, shall keep” our “hearts and minds through Christ Jesus” (Phil. 4:7). When Christ enters the heart it is always with the words, “Peace be unto you” (Luke 24:36). Thus, appropriately, ends the song of Zacharias. See on John 14:27.