Genesis 4:16-17, it says,
“16And Cain went out from the presence of the LORD, and dwelt in the land of Nod, on the east of Eden. 17And Cain knew his wife; and she conceived, and bare Enoch: and he builded a city, and called the name of the city, after the name of his son, Enoch.”
From this account, Cain’s family began in Nod (verse 16).
The name “Nod” is related to the words for “restless wanderer” (verse 14). It was the land of fugitives from God. Here Cain fathered a child, Enoch, and named a city after him. (No doubt Cain’s wife was a daughter of Adam; as can be seen in Genesis 5:4.
But we know that Adam and Eve had two sons: Cain and Abel. Cain killed Abel and was exiled by God. Then in Genesis 4:17, we read that Cain knew his wife.
So where did Cain get his wife from, since they were just boys in the home?
The answer is simple: Cain married either his sister or a niece.
Considering Genesis 5:3-5, we are told; “3When Adam had lived 130 years, he had a son in his own likeness, in his own image; and he named him Seth. 4After Seth was born, Adam lived 800 years and had other sons and daughters. 5Altogether, Adam lived 930 years, and then he died.” (NIV)
Since Adam lived 930 years (Genesisn5:5), it becomes easy for us to understand that he had lots of other children. The Genesis account did not tell us about the order of the births, nor does it tell us how old they were when they took wives. By having many children, it is certainly possible that there were many women around. This would mean that Cain married a sister, niece, a grand-niece, or some other relation, and their children had children, etc.
We can also verify this from secular history. Josephus, a first-century Jewish historian, compiled a history of humankind from creation, titled Antiquities of the Jews.
In chapter 2, section 1, he wrote of Adam and Eve, they had also daughters. In section 3, Josephus added about Adam: He had indeed many other children. As for the rest [besides Cain, Abel and Seth], it would be tedious to name them.
So, the writing of Josephus implies that Adam and Eve had a very large family! This view of Josephus is truly supported by the scriptures as we can see in Genesis 5:4.
Therefore, we can confidently say that Cain married one of his many sisters.
This we can confirm with the case of Abraham and Sarah in Genesis 20:1-12.
In verse 12, when telling Abimelech that Sarah is his sister, he explained “…And yet indeed she is my sister; she is the daughter of my father, but not the daughter of my mother; and she became my wife.”
So, we can see that the marriage of siblings was on until years later in Moses’ day, that God made a law forbidding marriage between close relatives (see Leviticus 18), but such a marriage was not illegal at the time Cain lived.
Cain’s wife had to have been one of the many daughters born to Adam and Eve. There were no health dangers to the offspring of close relatives at that time in history. While unthinkable in today’s world, there was no prohibition against marriage between siblings then.
When Abraham was asking Eleazer to take a wife for his son Isaac, he said;
Genesis 24:4 “You must go back to the country where I was born and get a wife for my son Isaac from among my relatives.” GNT
My country; Mesopotamia, called here Abraham’s country, because it was the place where the family of Haran, his brother, had settled; and where he himself had stayed a considerable time with his father Terah, in this family as well as in that of Nahor.
So, you see he sent him to his home and not to Rebecca’s homestead.
Therefore, as to the question, where did Cain get his wife from? The answer is, he married one of his siblings as relatives’ marriages were not prohibited then until, the time of Moses. Same with Abraham and Sarah as said before.
This again should put a stop to the issue of Abraham being a liar. It’s not true that Abraham lied, what he said was the truth. Sarah was not the daughter of Abraham’s mother but of his father and the marriage of siblings was permitted in his days. Stop accusing father Abraham of being a liar.
I urge you to study to show yourself approved unto God and stop peddling old fables as the Gospel.