How did Cain get married to his wife?

How did Cain get married to his wife?

This is an obvious question that might arise in the head of every Bible reader. When I read Genesis 4:16-17: ^“Then Cain went out from the presence of the Lord, and settled in the land of Nod, east of Eden. Cain had relations with his wife and she conceived and gave birth to Enoch; and he built a city, and called the name of the city Enoch, after the name of his son.”Here we do not find Cain went to Nod and found the wife there. Rather we can find the implication that he had a wife when he went to Nod and had relations with his wife. Let’s observe some more scripture: 

Genesis 2:7 "Then the Lord God formed man of dust from the ground and breathed into his nostrils the breath of life, and man became a living being." 

Genesis 2:21-22 So the Lord God caused a deep sleep to fall upon the man, and he slept; then He took one of his ribs and closed up the flesh at that place. The Lord God fashioned into a woman the rib which He had taken from the man and brought her to the man. 

In Genesis 1:28 God blessed them, and God said to them, Be fruitful and multiply, and fill the earth, and subdue it, and rule over the fish of the sea and over the birds of the sky and over every living thing that moves on the earth. We don't know when Cain killed Abel and also the Bible does not say how old Cain and Abel were? It is evident that they were not a teenager or young men but could be over forty years of age that means there could be a considerable number of people living at that time because the Bible says Adam and Eve had many sons and daughters in Genesis 5:4. This verse makes clear that they had more sons and daughters. When Seth was born Adam was one hundred and thirty years old. According to Jewish tradition, "they considered Adam had 33 sons and 23 daughters" which shows there were many people during that time. Finally, we can say Cain could have married would have been a sister or a niece.

Another question may arise in incest. This marriage during that time does not violate the commands of God because there was no such law given by God at that time. Later on, Moses wrote all the laws given by the Lord which condemns such a relationship in the book of Leviticus 18:18. From that day onwards, it is prohibited!