At the end of Genesis 2 we rejoice with Adam. The arrival of “woman” completes Adam and creation itself. Today we see that perverting God’s design in marriage brings terrible consequences.
The first detail we learn of Cain’s descendants is that “Lamech married two women” (v. 19). No specific prohibition against polygamy had been stated yet in Genesis, but it obviously violates the principle of two marriage partners becoming “one flesh” (2:24). The Trinitarian image of equality and mutual giving becomes impossible in polygamous relationships. Jealousy, suspicion, and pain are inevitable.
Context also indicates that polygamy has connections to Cain and his line making a name for themselves on earth (4:17). They showed, as commentator Matthew Henry noted, a “clever industriousness” about acquiring worldly things. Cain dwelled in Nod; his physical dislocation reflected spiritual turmoil, which his descendants turned to furious activity. Lamech’s marriages show this desire not to love and be loved but to possess and to make himself great.
If God intended marriage to reflect His loving purpose, then we can expect that introducing disorder to marriage will result in hatred and evil. Lamech’s wicked deeds knew no bounds. Cain succumbed to evil (4:7), but Lamech created a song to celebrate his murders (vv. 23–24). He failed to honor the life-giving purpose of marriage, and so cared nothing for the lives of others. The language of “seven times” and “seventy-seven times” uses a poetic formula to show he placed no limits on his self-assertion against others. Polygamy did not make Lamech this way, but we cannot miss the connection between his marriages and his violence.