The topic of incest in the Bible is a complex one that requires nuanced understanding. At different times in Scripture, we see instances where close relatives married each other or engaged in sexual relations. However, the Biblical authors don’t necessarily condone all of these situations. We have to analyze each case in its proper historical and cultural context.
First, it’s important to define what we mean by “incest.” Incest refers to sexual intimacy between close blood relatives. Many modern societies prohibit incest due to genetic concerns and for the sake of family order and ethics. The Bible prohibits some forms of incest but not others.
Incest in the early chapters of Genesis
In the early chapters of Genesis, we read about the origins of humanity and see marriages taking place between siblings and other close relations:
- Cain married his sister or another close relative (Genesis 4:17)
- Abraham married his half-sister Sarah (Genesis 20:2)
- Isaac married Rebekah, who was his first cousin once removed (Genesis 24:15)
- Jacob married two sisters, Leah and Rachel, who were his first cousins (Genesis 29:16-30)
At this point in biblical history, the human race was just beginning to spread out after the Flood. As commentators point out, it’s likely that siblings and close cousins married each other out of necessity. The gene pool was much more limited back then. Culturally, there was no taboo against close intermarriage.
We can speculate that God may have allowed intra-family marriages at this stage to rapidly grow the human population. As people lived for centuries, genetic abnormalities may not have been as much of an issue. But once key bloodlines were established and human society expanded, explicit prohibitions on incest appeared.
Mosaic Law’s incest prohibitions
In the Mosaic Law given to Israel, we see clear incest prohibitions laid out. Leviticus 18 and 20 forbid sexual relations with:
- Mother or stepmother (Leviticus 18:7)
- Sister or half sister (Leviticus 18:9)
- Grandchild (Leviticus 18:10)
- Aunt (Leviticus 18:12-13)
- Sister-in-law (Leviticus 18:16)
- Daughter-in-law (Leviticus 18:15)
- Sister of wife in polygamy (Leviticus 18:18)
Transgressing any of these brought the punishment of being “cut off” from the people (Leviticus 18:29). Scholars see the incest rules as meant to distinguish Israel from the surrounding pagan nations who practiced incest in their idolatrous worship.
In addition, the prohibitions promoted sexual purity, protected family structure, and prevented genetic problems. As a law code for a nation, the Mosaic prohibitions only forbid parent-child and sibling relations. Cousin relations are not included. The idea was to prevent the closest forms of incest.
Examples of incest that occurred
Despite the Mosaic prohibitions, we still find examples later in biblical history of incest occurring:
- Genesis 19:30-38 – Lot’s daughters got him drunk and slept with him, bearing the sons Moab and Ben-Ammi.
- 2 Samuel 13:1-15 – Amnon forced himself on his half-sister Tamar.
- 1 Corinthians 5:1 – A man in the Corinthian church was sleeping with his father’s wife.
In all of these cases, the incest is portrayed as deeply wrong. The actions have disastrous consequences. However, the biblical authors are simply recording sinful human behavior – not sanctioning it. These instances show that by biblical times, close incest was recognized as abhorrent even though it still occurred.
Did God allow incest between Adam and Eve’s children?
A common question is how Adam and Eve’s children could have reproduced without commiting incest. Commentators provide a few possible explanations:
- Adam and Eve likely had many other sons and daughters not recorded in Scripture (Genesis 5:4). So early siblings could have married undisclosed siblings.
- God may have supernaturally allowed close intermarriage early on to jumpstart the human population before the genetic harm caught up.
- Adam and Eve’s physical perfection was greater, so genetic defects from incest took many generations to accumulate.
We cannot know for sure. But what we do know is that God created one man and woman at the start. He blessed them to “be fruitful and multiply” (Genesis 1:28). For humanity to fulfill that command required some level of close intermarriage without today’s genetic risks.
Principles we can apply
When we survey the biblical evidence, several principles emerge that can inform our understanding of incest in Scripture:
- God’s moral standards for humanity develop progressively over time.
- Marriage between close genetic relatives was permitted or overlooked early in human history but later strongly condemned.
- Incestinous relationships reported in Scripture are never promoted, only reported as part of humanity’s sinfulness.
- The Mosaic Law prohibited incest to promote sexual purity, family order, and genetic health for Israel.
- All incest recorded in Scripture brought negative consequences, indicating its fundamentally sinful nature.
The biblical narrative traces an increasing sense of sexual ethics in human society over time. Incest gives way to new standards of sexual purity and wholeness based on God’s character and natural law. Scripture lays the groundwork for why the people of God abhor all forms of incest today.
Difficult questions on incest in Scripture
I’ll conclude by briefly noting two difficult questions readers may have:
1. Why does Mosaic Law permit cousin marriage?
The Mosaic incest prohibitions only forbid parent-child and sibling relations. Some claim that God prohibited all incest, so cousin marriage must be moral. But the Mosaic Law seems to be setting basic ground rules to distinguish Israel from surrounding cultures, not implying that cousin relations are perfectly ethical.
Strong biblical principles, like maintaining sexual purity and acting in love, should govern modern Christians’ views on cousin marriage.
2. Why does God bless children of incest like Moab?
WhenLot’s daughters commit incest, the resulting son Moab becomes a great nation (Genesis 19:37). Some ask why God would bless an incestuous lineage. First, the Moabite nation didn’t necessarily inherit the sins of its founders. Second, God shows patience and grace not to wipe out young nations that began unethically. He can bring redemptive good from humanity’s twisted ways.
Ultimately all nations need God’s mercy and guidance to live ethically. This was true of ancient Moab and remains so today.
The Bible’s treatment of incest is complex, with progressive development of standards and societal expectations. By grappling with the evidence in its context, we gain insight into both God’s ideals and his patience. Scripture points to ethical principles that can guide Christians in sexual ethics today.