So, people begin to invoke the name of the Lord. It took them long enough. You would think that the stories of Adam and Eve with their walks with God in the garden would have triggered their children and grandchildren to a devotion to the Lord which would have been obvious. But Scripture says that they began invoking the name of the Lord only at the end of chapter 4. What is sad in these stories is that the first accounts we have of humanity and their relationship with God is defined through sin. Adam and Eve sin, and so are punished and cast out. Cain sins and so is banished. But also in both of these cases we have God who ensures not only the protection of His children, but also their longevity and their security in perpetuity. God loves us even while we were yet sinners.
We find in this chapter the often misused quote: “Am I my brother’s keeper?” The answer to that questions is, of course, yes, of course. More often than not we misuse it to say that no, we are not responsible for our brother. But obviously in this context Cain was very much responsible for the demise of his brother so yes, he was at that point his brother’s keeper. Don’t let anyone use this quote to describe how they have either washed their hands of a situation or trying to shed any responsibility vis a vis another individual.