Cain was not alone when he left. He was with his wife. People often wonder who she was. It could not have been his sister,
they say. This is then used as proof that not all people descended from one pair of humans. It cannot be that all people descended from Adam and Eve.
The Bible is very clear about this. Every human being who lives and has lived on earth is a descendant of Adam and Eve. I will mention two texts in the Bible where the Holy Spirit is very clear about this. In Acts 17 we read that God made all things and then it says in Acts 17:26, “And he made from one man (“one blood,” KJV) every nation of mankind to live on all the face of the earth, having determined allotted periods and the boundaries of their dwelling place.” And in Genesis 3:20 we read that Adam gave his wife the name Eve.
The reason for this name was, because she was the mother of all living.
She is the mother of all mankind. These texts make it clear that in the beginning of history, it was necessary to marry each other as brother and sister. The Lord saw to it that this could happen in those days without adverse consequences.
Cain conceived his first child by his wife and named him Enoch. After his first child was born, Cain began to establish a permanent place for him and his family to live. The seed of the serpent began building a city of his own. It was not enough for Cain that he had received a sign from the Lord that would protect him. He sought protection in his own strength. We read in Genesis 4:18 that this family line continued to expand.
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.