The Prophetical Setting
as it is written in the book of the words of Isaiah the prophet, “The voice of one crying in the wilderness, ‘Make ready the way of the Lord, make His paths straight. Every ravine will be filled, and every mountain and hill will be brought low; the crooked will become straight, and the rough roads smooth; and all flesh will see the salvation of God.’ ” (3:4–6)
Nothing more convincingly demonstrates God’s control over history than fulfilled prophecy. One such prophecy is Isaiah 40:3–5, the subject of these verses. It was written in the book of the words of Isaiah the prophet seven centuries before John’s birth, and has immense theological and historical significance. John’s fulfillment of this prophecy also shows the continuity between his ministry and the Old Testament, something critically important if the Jewish people were to accept him as a prophet of God.
John perfectly fulfilled this prophecy. He was the voice … crying in the wilderness, where he lived most of his life and where he ministered (see the discussion of the geographical setting above). In keeping with his role as Messiah’s forerunner, John called on the people to make ready the way of the Lord, to make His paths straight. The imagery is of an Oriental monarch on a journey sending a messenger ahead of him to make sure the roads were cleared of debris or other hazards. In the process ravine[s] would be filled in, mountain[s] and hill[s] brought low, crooked paths made straight, and … rough roads made smooth.
Chapter 40, the source of this prophecy, is a pivotal point in the book of Isaiah. The first thirty-nine chapters focus largely on God’s coming judgments on Israel and the surrounding nations. The opening words of chapter 40, “ ‘Comfort, O comfort My people,’ says your God,” mark a dramatic change in tone. The message of Isaiah’s prophecy changed from judgment to salvation, which is the theme of the rest of the book. The same God who judged Israel for her sins will one day have mercy on her; His ultimate purpose for the nation is not judgment but the salvation of the believing remnant, based on His unmerited grace (cf. Rom. 11:1–32). The theme of God’s comforting of Israel runs throughout the last half of Isaiah’s prophecy (cf. 40:6–11, 28–31; 41:8–10, 13; 49:14–16; 51:1–3, 12; 52:9; 54:4–8; 57:18; 61:2; 66:12–13).
Ultimately, God’s comfort of Israel will culminate in the millennial kingdom. Human history will end when the Lord Jesus Christ establishes His earthly kingdom and reigns over the entire world (Ps. 2:6; Isa. 2:2; Jer. 33:15; Ezek. 34:23–24; Dan. 2:44–45; Hos. 3:5; Rev. 20:4–6). Politically, the millennial kingdom will be characterized by Christ’s universal, absolute, and righteous rule. Physically, the curse will be lifted, resulting in abundant provision, health, and long life for all. Spiritually, knowledge of the Lord will be universal (Isa. 11:9), and the believing remnant of Israel will be saved (Zech. 13:1, 8).
The words of Isaiah’s prophecy quoted here also serve as an analogy of the repentance John preached. The wilderness pictures the sinful heart, and repentance involves bringing to light the deep, dark things of the heart, pictured by filling in the ravines, and humbling human pride, depicted in the imagery of bringing low the mountains and hills. The crooked, deceitful, devious perverse things must be made straight, and any other rough places in the heart, whether self-love, love of money, love of the world, the lust of the flesh, indifference, or unbelief, must be smoothed out. Only then will the truly repentant see the salvation of God.
4–6 In its OT context, Isaiah 40:1–11 points to the arrival of the time of consolation. This eschatological tone is heightened in Malachi 3:1, where the way of the Lord is understood in a metaphorical sense. In the intertestamental period, Isaiah 40:3 became a symbol for the Jewish expectation of the end-times (e.g., Pss. Sol. 8:17; T. Mos. 10.1; 1 En. 1:6; cf. Carl J. Davis, The Name and Way of the Lord [JSNTSup 129; Sheffield: Sheffield Academic Press, 1996], 61–102). Isaiah 40:3 was also used by the community at Qumran as rationale for leading a separated life in the desert, where they believed they were preparing the way for the Lord by means of a constant reading of the law (1QS 8.12–16; 9.19–20).
For Matthew and Mark, the Isaiah passage was a clear prophecy of the ministry of John the Baptist. Luke includes more of the quotation than Matthew and Mark do. He first cites the extraordinary way in which, on the analogy of preparations made for a royal visitor, even the seemingly immovable must be removed to make way for the Lord. What needs removal is the sin of the people. Luke then concludes the Isaiah quotation with words that aptly describe his own evangelistic and theological conviction: “And all mankind will see God’s salvation.” Luke finds here, following the LXX, a biblical basis for his own universal concern and his central theme of salvation (cf. Morris, 95). The words concerning the appearance of God’s glory (Isa 40:5) are omitted. Luke does stress the glory of God often elsewhere, beginning with 2:14; but for some reason he apparently does not think it appropriate to stress it here.
The fact that Luke includes an extended quotation from Isaiah 40 also points to the significance of that chapter for the understanding of his entire gospel. As Isaiah 40 calls attention to the arrival of salvation for God’s people, the inclusion of the Gentiles, and the irresistible power of the Word, Luke carefully describes how this wider program is being fulfilled in the early Christian movement. Moreover, using the language of Isaiah 40:3, Luke later describes the church as the “Way” (Ac 9:2; 19:9, 23; 22:4; 24:14, 22; cf. Pao, 45–68).
3:4–6. Strange activities renew God’s prophetic actions and prepare the way for the Worthy One. At least, that is what John said. What authority did he have to make such claims? He rested completely on the authority of Scripture. As seen in chapters 1–2, Luke sought at each step to show that God’s good news is based on God’s old news. Isaiah 40:3–5 promised Old Testament Israel God’s deliverance from Babylonian exile along a path God would provide in the wilderness. John’s audience was promised an even greater experience of deliverance—salvation from sin. Such salvation was not a secret that God hid in the wilderness. It was a salvation God was proclaiming for all mankind (literally, “all flesh”).
God is consistent. He sticks to his purposes. He fulfills his word and then uses the word to bring new fulfillment and meaning to a new generation. For John’s generation, salvation came in the same setting as for the exiles: the wilderness. It came in a new way. People did not have to cross the dry desert between Babylon and Palestine. They had to cross the hard line from self-centered religious pride and piety to humble acceptance of baptism based on confession of their sins. Then they would be ready to see the salvation God had prepared in Jesus.
3:5 The effects of Christ’s coming are described as follows:
Every valley shall be filled—those who are truly repentant and humble would be saved and satisfied.
Every mountain and hill shall be brought low—people like the scribes and Pharisees, who were haughty and arrogant, would be humbled.
The crooked places shall be made straight—those who were dishonest, like the tax collectors, would have their characters straightened out.
The rough ways shall be made smooth—soldiers and others with rough, crude temperaments would be tamed and refined.
3:6 A final result would be that all flesh—both Jews and Gentiles—would see the salvation of God. In His First Advent the offer of salvation went out to all men, though not all received Him. When He comes back to reign, this verse will have its complete fulfillment. Then all Israel will be saved, and the Gentiles too will share in the blessings of His glorious kingdom.
3:4–6Prepare the way: This citation from Is. 40:3–5 declares the coming of God’s deliverance. Luke cites the text more fully than Matthew or Mark. He carries the passage through to its mention of salvation being seen by all flesh (v. 6), thus highlighting that the gospel is for all people. The preparation for the arrival of a king typically meant that a road was prepared for his journey. This is what Isaiah compares to the arrival of God’s salvation, both after the Babylonian captivity and in God’s final work of salvation. Isaiah 40 introduces the entirety of Is. 40–66, which discusses both these events (Is. 49:8–11; 52:11, 12; 62:6–10, especially 57:14–17). One event pictures, to a lesser degree, the other greater event, since God works in patterns. The Gospel writers compare John to the one who announces that the time is right to get ready for such an arrival. The preparation alluded to here is spiritual, the readiness of the heart, as his preaching shows.
3:3–6. John’s message was a baptism of repentance for the forgiveness of sins. John’s baptism was associated with repentance, that is, it outwardly pictured an inner change of heart. The word “for” (eis) refers back to the whole “baptism of repentance.” The baptism did not save anyone, as is clear from what follows (vv. 7–14). Repentance was “unto” (lit. rendering of eis; cf. comments on Acts 2:38) or resulted in sins forgiven. Since John’s function was to be Christ’s forerunner, so also his baptism prefigured a different baptism (Luke 3:16). Luke noted that John’s baptizing work was in the country around (perichōron) the Jordan. Because John was visibly taking on himself the role of Elijah, it is possible that he picked this area on the lower Jordan because that was where Elijah spent his last days (cf. 2 Kings 2:1–13). Luke quoted from Isaiah 40:3–5 concerning John’s ministry. Isaiah was writing of God’s smoothing the way for the return of the exiles from Babylon to Judah. But all three Synoptic Gospel writers applied Isaiah’s words to John the Baptist.
Isaiah wrote, “A voice of one calling: ‘In the desert, prepare the way for the Lord.’ ” But Matthew, Mark, and Luke each wrote, A voice of one calling in the desert—the words “in the desert” going with the “voice” rather than with the preparing of the way. Why? Because they quoted from the Septuagint. Of course both are true—the voice (of John the Baptist) was in the desert, and the desert was to be smoothed.
When a king traveled the desert, workmen preceded him to clear debris and smooth out the roads to make his trip easier. In Luke the leveling of the land was a figurative expression denoting that the way of the Messiah would be made smooth because through John a large number of people were ready to receive Jesus’ message (cf. Luke 1:17).
Typical of Luke’s emphasis on the universal availability of the gospel are his words in 3:6, And all mankind will see God’s salvation.
 MacArthur, J. F., Jr. (2009). Luke 1–5 (pp. 210–211). Chicago: Moody Publishers.
 Liefeld, W. L., & Pao, D. W. (2007). Luke. In T. Longman III & D. E. Garland (Eds.), The Expositor’s Bible Commentary: Luke–Acts (Revised Edition) (Vol. 10, p. 89). Grand Rapids, MI: Zondervan.
 Butler, T. C. (2000). Luke (Vol. 3, pp. 47–48). Nashville, TN: Broadman & Holman Publishers.
 MacDonald, W. (1995). Believer’s Bible Commentary: Old and New Testaments. (A. Farstad, Ed.) (p. 1377). Nashville: Thomas Nelson.
 Radmacher, E. D., Allen, R. B., & House, H. W. (1999). Nelson’s new illustrated Bible commentary (p. 1255). Nashville: T. Nelson Publishers.
 Martin, J. A. (1985). Luke. In J. F. Walvoord & R. B. Zuck (Eds.), The Bible Knowledge Commentary: An Exposition of the Scriptures (Vol. 2, pp. 210–211). Wheaton, IL: Victor Books.