Question: Could you please tell me something about the symbolism of the "Lamb of God" in Revelation and of symbolism in general in that book such as the New Jerusalem (its walls and gates, etc.)?
Response: Jesus is "the lamb who takes away the sin of the world" (Jn.1:29; cf. Jn.1:36; 1Pet.1:19; Is.53:7). He is the one whom all the Old Testament sacrifices prefigure, so that "lamb" is a perfect description of Him: just as lambs were slaughtered and sacrificed and their blood used for symbolic purification, so the actual death of our Savior on the cross - His blood, so to speak - cleanses us from all sin in reality. The title "Lamb of God" always puts this symbolism (of Christ's death on our behalf) in the forefront. The Revelation of Christ (the Greek title of the book) is just that, an "unveiling" of Christ, for at this present moment the world has not seen Him in His glory; that glory is intimately connected with the victory He won at the cross, so that John, under the guidance of the Spirit, saw fit to make ample use of the title "Lamb of God" in his descriptions of our glorified Savior Jesus Christ. Revelation, moreover, is a prophetic unveiling of future events, accomplished with much symbolism (such as the dragon for Satan); these symbols paint for us an even more powerful and vivid picture of the realities to come than literal description could have done. We see the literal description of our glorified Lord in chapter one, but His later description as the Lamb of God not only recalls this literal picture but also brings to mind His purity and humility of life during His first advent, and His blessed sacrifice on our behalf.
It is important to remember that Revelation prophesies reality, even though it does so with symbolism in some places. Not everything is symbolic (lambs and dragons yes, people and cities no). There will in fact be a New Jerusalem which we believers will populate, and it will look like Rev.21-22 says. The wall is real, the gates are real, the gold pavement is real, the precious stones are real. We can see in the wall a separation of the holy and the profane (cf. Rev.22:14-15), in the open gates, our eternal access to God the Father and the Son and the security that will obtain forever (so that there will never be a need to close them), and we can relate the precious stones to the various tribes of Israel (to which nation we gentiles have been joined by grace: Rom.11:11-24; Eph.2:11-22). This last topic is covered in some detail in The Satanic Rebellion, Background to the Tribulation, in Part 4, section III.3.b.2, and Part 1, section 3.f.
Here is what I have written on this subject in the upcoming part 4A of Bible Basics, Christology:
The Lamb of God: The title "Lamb of God" reminds us of the Old Testament sacrifices regarding sin (which all speak of our Lord's death on the cross), and calls attention to Jesus as the only perfect substitute and sacrifice for our sins, a "lamb without blemish" (1Pet.1:19; cf. Is.53:7) who took away "the sins of the world" (Jn.1:29). Jesus, of course, offered up His life, not literally His blood (cf. Heb.8:3: "something to offer"). For "the blood of Christ" is a symbol of Jesus' sacrifice just as "the Lamb of God" is a title symbolic of His sacrifice in being judged for our sins in the darkness on the cross (2Cor.5:21; 1Pet.2:24). This title figures prominently in the book of Revelation because it is through His sacrificial death on our behalf that He has won the right to rule the world (Rev.5:6; 5:8; 5:12-13; 6:16; 7:9-10; 7:14; 12:11; 13:8; 13:11; 14:1; 14:4; 14:10; 15:3; 17:14; 19:7; 19:9; 21:9; 21:14; 21:22-23; 21:27; 22:1; 22:3).
For more on the Lamb of God, please also see the following link:
Coming Tribulation part 2B: "The Lamb and The Scroll: Revelation 5:1-14"
And please see also this link:
The Names of Jesus Christ Reflect His Perfect Person and His Perfect Work (from BB 4A: Christology)
Hope this is of help.
Yours in Christ,