WHERE CAIN’S WIFE CAME FROM

Before Seth was born in Gen 4:25, Cain had a whole generation of children and grandchildren according to Genesis 4:17-24. So, we see a Generation before Seth. Therefore, when Cain said all those who meet him shall slay him, he was referring to his own descendants. This made him fearful to leave his home; he knew what he was.
 
Gen 4:16-17, says, “And Cain went out from the presence of the LORD, and dwelt in the land of Nod, on the east of Eden. And Cain knew his wife; and she conceived, and bare Enoch”
The bible does not say that Cain found the woman in Nod, rather, the scripture says, “he Knew". This word “knew” means he had sexual intercourse with his wife in the land of Nod; she conceived and had a son.
So, where did he get the wife?
With scriptural understanding in Genesis 5, Cain marry one of his family members; either sister or niece.
Let us look at the facts in scriptures.
Here, we are dealing with history; but the information that’s given is not given in an orderly manner of what happened first, second and third. E.g., in Gen 5:7 it says, “And Seth lived eight hundred and seven years after he begat Enosh; and he begat sons and daughters:” 
It sounds like the scripture is saying, Seth begat sons and daughters when he reached eight hundred and seven years after Enosh’s birth, But No! the same structure of speaking is seen in Gen 5:4, “And the days of Adam after he had begotten Seth were eight hundred years: and he begat sons and daughters” Again, were the sons and daughters born after Seth’s birth? No!
 
The term, “and he begat sons and daughters” after pronouncing Seth’s birth is NOT telling you of the time in which he begat them; but it’s telling you that he begat other children during his lifetime.  
Therefore, if the term, “and he begat sons and daughters,” is telling you of the timeframe of the children’s birth [based on its time placement in scriptures] this would mean that the children were born after Seth was born, making things more complicated.
 
This is confirmed in scriptures where it says, Gen 4:16, “And Cain…dwelt in the land of Nod, And Cain knew his wife; and she conceived, and bare Enoch”. Be mindful, this finding of a wife happened long before Gen 5:4 where it says Seth was born and Adam had other sons and daughters.” 
 
But Gen 4:25 gives us better insight to understand. Gen 4:25, “And Adam knew his wife again; and she BARE A SON, and called his name Seth”.
It spoke of a second conception but specified “A SON”. It did not say children; but Son.
This means, the daughters most likely were born before Seth, confirming Gen 5:4 and explaining Gen 4:17, [And Cain knew his wife]; but were not mentioned, as it was not important to the message of God.
Seth was born when Adam was 130 years old. 130 years is enough time for Adam to have other children. Within this 130 years, Adam and Eve's children grew. When Cain left, he took one of these women to be his wife and went to the land of Nod.