City Building
17 Cain knew his wife, and she conceived and bore Enoch. When he built a city, he called the name of the city after the name of his son, Enoch.
After the death of Abel and after moving east out of Eden into the land of Nod, Cain has a child, Enoch, and builds a city which he names after that son. There is an interesting association here to the legend of Rome's founding. According to that legend, the founder of Rome, Romulus, murdered his brother Remus and founded the city of Rome after that murder. It is likely that this legend is a half-remembered version of the founding of the city of Enoch which had been passed down since before the flood.
From the perspective of the Biblical narrative itself, a few observations can be made at this point. First, it appears that Cain either was already married or married soon after the murder of Abel and had his first child, the first grandchild of Adam and Eve (or at least the first recorded). The question is raised, of course, where did this woman come from? It is not recorded that Adam and Eve had had more children, but it seems unavoidably the case that they did in fact have many other children around the same time as Cain and Abel. It is possible that most of the children were female and only the male children were recorded. Given the nature of mankind, it is quite possible for a single man to have multiple women as wives and to bear children with all of them. The reverse is not true. Since family lines of authority pass down from the male line instead of the female, it is possible that we have only recorded the primary male lines for that reason.
It is also possible that God chose only to record the lines of descent that most clearly pictured the distinction between the "seed of the serpent" and "the seed of the woman". We see what happens with Cain's line in these next verses, and in the chapter following, we will find that Seth's line produces Noah who, along with his family, are the sole individuals God saves from the flood and the ultimate ancestor of Christ himself.
Given that this conflict between Christ and the Devil is the conflict that is set up in Genesis 3, it makes sense that God would choose to emphasize the continuing animosity between the line that leads to Christ and the various wicked men that are born throughout the ages. While God continues to cut off the family lines of the wicked, the fundamental corruption introduced when Adam abdicated his authority to the Devil means that humankind continues to generate wicked men who oppose the "seed of the woman": "enemies of the cross of Christ" (Phil 3:18-19).
Cain also essentially had to build a city, in that he was no longer able to work the ground since the curse from God lay upon him. He becomes a sort of king, it would seem. Some have claimed that cities are inherently bad, as the first recorded city is made by one of the more vile figures in Scripture. This does not resonate with the final chapters of the Bible, where the New Jerusalem symbolizes the redeemed people of God.
Rather it would appear the significance is typological. The first city is a city of wickedness and evil, founded by an evil man. The last city is a city of redemption, righteousness and light, founded by the perfect God-man, Christ.
Polygamy
18 To Enoch was born Irad, and Irad fathered Mehujael, and Mehujael fathered Methushael, and Methushael fathered Lamech. 19 And Lamech took two wives. The name of the one was Adah, and the name of the other Zillah.
Lamech is the first instance we have of polygamy. It's not certain that he was the first to practice it, but the fact that it was recorded in this way is likely an indication that he was the first. This pattern continues throughout much of Genesis, as even the righteous patriarchs often take more than one wife.
It is reasonable to ask the question of when polygamy should have really been understood to be morally wrong. Christ refers to the verses at the end of Genesis 2 (a man shall leave his father and mother and be joined to his wife) as his proof text against divorce and Christian teaching has often also used this as the fundamental basis that polygamy is morally wrong as well.
The difficulty arises in that God's law does not clearly forbid polygamy under Moses, and in fact, provides case law to cover it; thus we must understand it in the same way that we understand divorce laws and slavery laws.
The creational nature of marriage, being a single man married to a single woman, is enough for Christ to explain the immorality of divorce, and is enough for us to understand the immorality of polygamy. While the law of Moses does not directly condemn polygamy in all cases, we can use our wisdom to understand that Leviticus 18:18 and Deuteronomy 17:17, when properly applied, also condemn polygamy.
Leviticus 18:18 Nor shall you take a woman as a rival to her sister, to uncover her nakedness while the other is alive.
Deuteronomy 17:17 Neither shall he multiply wives for himself, lest his heart turn away; nor shall he greatly multiply silver and gold for himself.
In the first passage, Leviticus, we find that women must not be taken as rivals to their sister. While this could legally be applied to the physical family, we also understand that we are all brothers and sisters in Christ, and thus any two Christian women (the only kind of woman it is permissible to marry) should not be taken both as wives. The same was frankly true of the Israelites at the time, though this is not a proper place for elucidation of the law and its application.
In the second passage, it tells us that kings are expressly forbidden to take multiple wives. As the nation of Israel, and its fulfillment, the church, are intended to be nations of priestly kings, this should be most properly applied to every citizen of Israel and every member of the church.
We also know that Christ's single bride is the church, and that this is primarily what marriage most truly is. Our marriages are an analogy to Christ's relationship with his church, a shadow and a picture. It might be tempting to thus say that Christ is polygamous, since the church is made up of so many different individuals, but this is part of the incorrect interpretation of the "bride of Christ" imagery. We are not individually the brides of Christ, nor is the church a simple collection of saved individuals. The church exists as an organic whole and it is that whole that is the bride of Christ. The mystery is great, as Paul said, and not easy to wrap our heads around.
One point of application we can learn from this, however, is that the semi-erotic "Jesus is my boyfriend" imagery of certain Christian teachings and hymns over the years is entirely inappropriate. The fact that the church is feminine and a bride does not in any way change the masculine and non-erotic relationship that men have with Christ as brothers. Truly, all family relationships shed light on an aspect of the way God relates to us, but driving the analogy too far creates bizarre and inappropriate understandings.
Technology
20 Adah bore Jabal; he was the father of those who dwell in tents and have livestock. 21 His brother's name was Jubal; he was the father of all those who play the lyre and pipe. 22 Zillah also bore Tubal-cain; he was the forger of all instruments of bronze and iron. The sister of Tubal-cain was Naamah.
The first technological creations recorded were the creations of the line of Cain. This has led some commentators to claim that technology is inherently a bad thing. Rightly understood, technology is a form of wealth and thus has capacity for great evil and great good. It is possible that the technological wealth generated by Cain's line was one of the things that led their hearts astray from the Lord, as they learned to trust in their great wealth instead of in the Lord their God.
But lyre and pipe and other instruments are used in the worship of the Lord in later times and thus we cannot say that the creation itself was a problem. It is reasonable to be suspicious of new technology in the same way that we would be suspicious of our own hearts when we are given a large inheritance. Our overriding concern ought not to be to eschew it or somehow "limit" it, but to make sure that it is rightly stewarded such that its use leads to a greater glorification of God.
I also reflect on a fascinating consideration regarding Tolkein's view of technology and magic. He was not a fan of urbanization or mechanization and indeed the war machine of Sauron is a tacit condemnation of the practice. In Tolkein's world there are two forms of "magic". There is what is practiced by the elves, where they work with the world in its natural form to enhance its beauty, and there is the magic of the Enemy, which corrupts and twists and attempts to control the natural world.
It is worth noting that this is probably precisely the sort of distinction we should make regarding technology. A Christian society ought to be one where natural beauty is enhanced and highlighted, not paved over and destroyed.
Vengeance
23 Lamech said to his wives:
“Adah and Zillah, hear my voice; you wives of Lamech, listen to what I say: I have killed a man for wounding me, a young man for striking me. 24 If Cain's revenge is sevenfold, then Lamech's is seventy-sevenfold.”
Lamech finishes this chapter with a threat to those who would oppose him. The violence and anger of Cain has matured after six generations. Now he is not simply willing to kill, but seems to do so even at minor offenses. While God promised to offer vengeance on any who slew Cain, Lamech threatens to take that vengeance himself, taking the prerogative of God. Romans 12:19 cautions us against this sort of personal vengeance-taking.
When we consider the desire for vengeance, we must understand that, at its root, the desire is a desire for justice as we understand it. Anger is the emotion that drives this. Anger itself is not evil, as we know that the Lord is made angry. The emotional reaction to injustice is part of our image-bearing of God.
The problem is that anger often turns to vengeance, although often not murderous vengeance. But each time that we attempt to cause the appropriate evil to befall someone who has done evil to us or to someone we love, we are engaging in vengeance. The Bible does not allow for vengeance to be taken in this manner.
This does not mean that all crimes go unpunished. The Lord has sovereignly administered many governments in this world, family, church and civil and we should look to the appropriate authority figures to administer justice in the name of God. Those who are placed in a position to administer godly justice are described as God's servants (Rom 13:4). However, if you are in a position to administer the justice required, you must still take care that you do not allow the desire for disproportionate vengeance to overtake your wisdom. Nor is this a blank check for personal vengeance (Rom 12:19 again).
There is much nuance as to who is allowed to take action to right a wrong and in what manner and this is explored in the books of the law. However, it is also worth noting that at this time it appears that the death penalty was not yet allowed to mankind. After the Flood, God gives Noah the authority and requirement to use the death penalty, but it would seem that prior to the Flood, any killing of another human being, even for egregious crimes, was not something God had condoned. Obviously, we have nothing in our text thus far that would lead us to believe that killing was acceptable, and this may be why God makes it explicit in Genesis 9.
Conclusion
This is a substantively shorter and less theologically dense portion of Scripture that we have been analyzing. We are beginning to see the creation of a world that is more fully formed, with many people and with the sorts of civilizational developments that we associate with human society. Of course, this world is hurtling toward its end in judgment, so we also see the inclination toward evil that Cain's line develops into.