Why did God allow incest in the Bible?

Any sexual relation with a blood relative is firmly forbidden (vv. 6-18). Even secular governments recognize the morality of this, so that incest is illegal. Abraham, married his half-sister (Gen. 20:11-12), but this was early in human history, when there was not the same danger of children being badly affected. “The laws of heredity show that in a fallen race, the inheritance of disease to which all are liable is intensified when similar tendencies are found in both parents” (Numerical Bible — Genesis — page 349). Time only increases the weakness that such disease brings in any genetic line, and of course this would be doubly increased by the marriage of two from the same line.

How much better it would have been for Lot to have heeded the word of God's messengers, "Escape to the mountain"; it would have preserved him from the fear that overtook him in Zoar, and he would have known the mountain retreat as God's place of shelter, rather than his cave of shame. So often we think we know what is best for us, and turn away from what God enjoins, only to prove at length our own folly, and to have lost what God had in His mercy prepared for us. Had Lot sought the face of God he might have found the mountain a place of communion, but instead it is the scene of his lasting reproach. Separation from the world does not necessarily mean communion with God, for the gross corruptions of the world can be found within the seclusion of a monastery, or a nunnery, just as in the midst of a wicked city. The influences of Sodom had left their mark on the daughters of Lot, for they brought to the cave what they had learned there. They had not learned that God could provide a generation for Lot, if it were His will, without resorting to such debasing means. Abraham and Sarah, Manoah and his wife, and Zacharias and Elizabeth, all proved how God could intervene to provide children for them, in His own way.

Surrounded as Israel were with all the filth of heathendom, they were to be for Jehovah, and to keep His commandments and His ordinances. As His people, He told them what they were to do, and what they were to be. Certain instructions for their camp life to guard them from idolatry we have looked at in the previous chapter of this book. We now approach the chapter which treats of marriage, for, as Jehovah's people, He prescribed within what degrees of consanguinity or affinity, such unions would be deemed unlawful, and precursors of divine chastisement. Till Israel came to Sinai, we have no hint of any marriage law laid down by God. Before the flood, and certainly in the days of Cain, what the Levitical law ruled as incest, was lawful. Men married their sisters. And even in Abraham's day such unions do not seem to have been unlawful. Sarah was Abraham's half sister. Jochebed was Amram's own aunt, his father's sister. By the the law of Leviticus, such unions as Abraham and Sarah, Amram and Jochebed, and Jacob and Rachel, were distinctly forbidden (18:11-12, 18).

It is beautiful to trace the unbending authority of revelation. Moses was inspired to interdict such a marriage as that of Abraham and Sarah, to speak of no more. There is no apology for the past, though of course the guilt would have been aggravated for the future.

(2) In the next place, we find the limit imposed upon marriage in regard to blood-relationship. Here abundant reasons evidence that character of the divine law which has been announced above. The laws of heredity show that in a fallen race, the inheritance of disease to which all are liable is intensified where similar tendencies are found in both parents. In the need also of looking outside the circle of near relationship for partners, the selfishness of man finds a divine restraint, and the bonds which unite man with man at large are strengthened and multiplied. Besides which the intimacies of the home and family are guarded from abuse.

Lev. 18:6-18.

The divine prohibition in this portion of our chapter refers to near relations and rests simply on the divine will and authority: "I am Jehovah." Marriage was not, save at the beginning, to unite "one's own flesh," naturally united or near already.

"6 None of you shall approach to all (or, any) flesh of his flesh to uncover nakedness: I [am] Jehovah. 7 The nakedness of thy father, and the nakedness of thy mother, shalt thou not uncover (she [is] thy mother); thou shalt not uncover her nakedness. 8 The nakedness of thy father's wife shalt thou not uncover: it [is] thy father's nakedness. 9 The nakedness of thy sister, daughter of thy father, or daughter of thy mother, born at home or born abroad, their nakedness thou shalt not uncover. 10 The nakedness of thy son's daughter or of thy daughter's daughter, their nakedness thou shalt not uncover; for theirs [is] thy nakedness. 11 The nakedness of thy father's wife's daughter, begotten of thy father (she [is] thy sister), thou shalt not uncover her nakedness. 12 The nakedness of thy father's sister shalt thou not uncover; she [is] thy father's own flesh. 13 The nakedness of thy mother's sister shalt thou not uncover; for she [is] thy mother's own flesh. 14 The nakedness of thy father's brother shalt thou not uncover; thou shalt not approach his wife: she [is] thine aunt. 15 The nakedness of thy daughter-in-law shalt thou not uncover (she [is] thy son's wife); thou shalt not uncover her nakedness. 16 The nakedness of thy brother's wife shalt thou not uncover; it [is] thy brother's nakedness. 17 The nakedness of a woman and her daughter shalt thou not uncover; thou shalt not take her son's daughter, nor her daughter's daughter, to uncover her nakedness (they are] her own flesh): it [is] wickedness. 18 And thou shalt not take a wife to her sister, to vex [her] (or, be a rival), to uncover her nakedness, beside her during her life" (vers. 6-18).

Leviticus 18 keeps them from dishonouring themselves in the things which belong to nature itself — to what man ought to be in his natural relations, that he might not dishonour himself. Man ought not to do it; but, not having honoured God, he has been left to dishonour himself (compare Rom. 1). The people of God, being brought into nearness to Him, are taught on this subject. They were separated from the evil of the world they were called out of, and the reckless profligacy into which Satan had driven degraded man as his sport. Verse 6 is the great principle which is insisted on in the chapter — not to confound the intimacies of marriage with the confidence of natural relationship. Those things are forbidden into which, in the satanic and unnatural indulgence of flesh, Satan plunged man, and to which God had given them up to work all uncleanness with greediness. The comeliness of nature is maintained; what is defiling forbidden. Jehovah's statutes and judgments were to guide them: man in probation walking in them would live.

Lot had pled to go to Zoar, but after Sodom's destruction he became afraid to remain in Zoar, and took the angels' previous advice to flee to the mountains. Abraham walked generally by faith, but Lot had not learned such a lesson: he was moved at this time by fear. He found a cave in which he lived with his daughters. How deeply impoverished he had become! Lot's history is a warning indeed to every child of God, that friendship with the world will lead, not necessarily to material poverty, but always to spiritual poverty.

The scheming of Lot's daughters to have children by their father is a sad comment on what they had learned in Sodom (vv. 31-32) Also, Lot had so sunk down in unconcern about the honor of the Lord that he would allow himself to become so drunk as to not realize what he was doing. Nor was this only once, but a second time on the following night (vv. 34-35). We may wonder even at the survival of the children, but the first became the father of the Moabite nation, the second the father of the Ammonites, both of them proving to be troublesome enemies of Israel.

Though saved from the doom of Sodom, poor Lot is still the victim of fear. The very city of his choice he fears to dwell in, so he falls back on the mountain to which he had been told to flee. But even so, he goes to the mountain driven by fear of men rather than led by faith in God. There he becomes involved in the infamy of his daughters to pass from the history with no record of his end, leaving behind a posterity that becomes the constant enemy of God's people.

This then was the end of the place where Lot had lived and laboured, or at least talked. He was as little in the secret of Jehovah as the men of Sodom, though no doubt he was vexed, or rather (as scripture so pregnantly tells us) the righteous man vexed his righteous soul from day to day. But God never called Lot to Sodom, as He had called Abraham out of Ur of the Chaldees to Canaan. Abraham's groans were gracious, and had profitable fruit; Lot's were not without his own fault and torment, groans barren even for himself. Abraham is attracted to the place where he had enjoyed the presence and converse of Jehovah, and looks down on the scene of desolation which attested in its solemn way what it is to hate Jehovah, and what to love Him. And there Lot too goes up out of Zoar: afraid to go at God's bidding when there was no ground for fear there, afraid longer to stay in Zoar, and not afraid to go where and when he had feared most of all, had he been aware into what a snare he was about to be caught by wine and women — alas! his own daughters. Such was the end of him who would needs be a judge in Sodom, but only the beginning of those who should inflict sorrowful results on the children of Abraham throughout their history, till that day come when Sodom's doom finds its antitype, and the Branch out of Jesse's roots shall reign, and Moab, with Edom, shall be the laying on of Israel's hand, and the sons of Ammon their obedience (Isa. 11:14).