Hello FOTOP,
Since the Bible does not mention Abel as having a wife (Possibly killed before he married) you likely meant to ask "Who was Cain's wife?" since we read:
Genesis 4:17 (New International Version)
17 Cain lay with his wife, and she became pregnant and gave birth to Enoch. Cain was then building a city, and he named it after his son Enoch.
This Question Was Asked in the Scopes Monkey Trial
This very important question made its way into the State Court of Tennessee during 1925 in the "Scopes Trial" State v. Scopes, Scopes v. State. Today it’s also remembered as the "Scopes Monkey Trial".
It was an American legal case that tested the Butler Act, which made it unlawful, in any state-funded educational establishment in Tennessee, "to teach any theory that denies the story of the Divine Creation of man as taught in the Bible, and to teach instead that man has descended from a lower order of animals." The case was a critical turning point in the United States' creation-evolution controversy.
The trial became more dramatic where William Jennings Bryan, the prosecutor who stood for the Christian faith, failed to answer the question about Cain’s wife posed by the ACLU lawyer Clarence Darrow. Consider the following excerpt from the trial record as Darrow interrogates Bryan:
Q—Did you ever discover where Cain got his wife?
A—No, sir; I leave the agnostics to hunt for her.
Q—You have never found out?
A—I have never tried to find.
Q—You have never tried to find?
A—No.
Q—The Bible says he got one doesn’t it? Were there other people on the earth at that time?
A—I cannot say.
Q—You cannot say. Did that ever enter your consideration?
A—Never bothered me.
Q—There were no others recorded, but Cain got a wife.
A—That is what the Bible says.
Q—Where she came from you do not know.
The typical answer to this question from a variety of Biblical scholars are either
1) Adam & Eve had additional children who don't happen to be named in the Bible (certainly a possibility, given how seldom women and daughters are mentioned by name)
And/Or
2) Other humans existed elsewhere, as evidenced by Cain's lament that he would be treated as a murderer in exile from the Garden of Eden... where he eventually picked up a wife.
We first need to rule out that there were other people on the earth who were not descendants of Adam and Eve. The gospel adheres to the fact that all human beings are descendants of one man and one woman (Adam and Eve).
Romans 5:12-13 (New International Version)
12Therefore, just as sin entered the world through one man, and death through sin, and in this way death came to all men, because all sinned— 13for before the law was given, sin was in the world. But sin is not taken into account when there is no law.
We inherited this sin nature thru the blood line going back to Adam and Eve and not thru another set of un-related people. This is a major reason why we need to be able to account for Cain’s wife and show clearly she was a descendant of Adam and Eve.
Cain was the first child of Adam and Eve recorded in Scripture. He had two brothers whose names were recorded in the biblical record; Abel and Seth were part of the first generation of children born on this Earth. Even though only these three males are mentioned by name, Adam and Eve had other children.
Genesis 4:1-2 (New International Version)
1 Adam lay with his wife Eve, and she became pregnant and gave birth to Cain. She said, "With the help of the LORD I have brought forth a man." 2 Later she gave birth to his brother Abel. Now Abel kept flocks, and Cain worked the soil.
Genesis 4:25 (New International Version)
25 Adam lay with his wife again, and she gave birth to a son and named him Seth, saying, "God has granted me another child in place of Abel, since Cain killed him."
Genesis 5:3-5 (New International Version)
3 When Adam had lived 130 years, he had a son in his own likeness, in his own image; and he named him Seth. 4 After Seth was born, Adam lived 800 years and had other sons and daughters. 5 Altogether, Adam lived 930 years, and then he died.
The bible does not say when they were each born. In fact many other children could have been born in the 130 years before Seth was born as well as the 800 after his birth. The Jewish historian Josephus wrote that, “The number of Adam’s children, as says the old tradition, was thirty-three sons and twenty-three daughters.” It would seem reasonable to suggest there were many! Remember, they were commanded to ‘Be fruitful, and multiply’
Genesis 1:28 (New International Version)
28 God blessed them and said to them, "Be fruitful and increase in number; fill the earth and subdue it. Rule over the fish of the sea and the birds of the air and over every living creature that moves on the ground."
Civilizations and Laws
Researching studies of early civilizations: we find that it is widely accepted that the Egyptians were known to marry brother/sister even son/mother. Therefore it is probable that Adam and Eve and their offspring were the first to initiate this practice. Today the idea of a marriage between blood relatives procreating is both a social stigma and detestable thought for a good reason. God has forbidden it.
Leviticus 18 (New International Version)
Unlawful Sexual Relations
1 The LORD said to Moses, 2 "Speak to the Israelites and say to them: 'I am the LORD your God. 3 You must not do as they do in Egypt, where you used to live, and you must not do as they do in the land of Canaan, where I am bringing you. Do not follow their practices. 4 You must obey my laws and be careful to follow my decrees. I am the LORD your God. 5 Keep my decrees and laws, for the man who obeys them will live by them. I am the LORD.
6 No one is to approach any close relative to have sexual relations. I am the LORD.
7 Do not dishonor your father by having sexual relations with your mother. She is your mother; do not have relations with her.
8 Do not have sexual relations with your father's wife; that would dishonor your father.
9 Do not have sexual relations with your sister, either your father's daughter or your mother's daughter, whether she was born in the same home or elsewhere.
10 Do not have sexual relations with your son's daughter or your daughter's daughter; that would dishonor you.
11 Do not have sexual relations with the daughter of your father's wife, born to your father; she is your sister.
12 Do not have sexual relations with your father's sister; she is your father's close relative.
13 Do not have sexual relations with your mother's sister, because she is your mother's close relative.
14 Do not dishonor your father's brother by approaching his wife to have sexual relations; she is your aunt.
15 Do not have sexual relations with your daughter-in-law. She is your son's wife; do not have relations with her.
16 Do not have sexual relations with your brother's wife; that would dishonor your brother.
17 Do not have sexual relations with both a woman and her daughter. Do not have sexual relations with either her son's daughter or her daughter's daughter; they are her close relatives. That is wickedness.
18 Do not take your wife's sister as a rival wife and have sexual relations with her while your wife is living.
Truth and Medical Consequences
Why after so many years of this practice did God forbid it? The reason primarily was medical. Think of Adam and Eve and their progeny as 'purebreds'; their genome was perfect. Remember that initially they were made immortal. Their DNA would be passed on throughout eternity undamaged to their offspring. They were created perfect in a perfect environment.
However, they rebelled and with that they began to die with their bodies/DNA began to fall apart. The medical consequences begin to accumulate. Looking at the life spans of some of Adam's children- and this is after the fall- they get close to a thousand years- and that's after the damage. After the flood, there is a huge genetic turn for the worse, and life spans drop below 100 years, as they are today. Mankind began to find that the results of the DNA defects in children were greater and more serious when blood relatives married. Eventually laws were introduced in many countries to prevent this, long after God gave his own law.
So we need to conclude then that Cain as well as his brothers would have married their sisters, or nieces. It would have been proper at that time, since the Earth's population was relatively sparse and the DNA stable enough to permit it. The human race was to be proliferated according to God's purpose.
God Bless,
Cartoonbug