Marriages between Israelites were directed by law, and all incestuous relationships were outlawed (Lev. 18:6-8; 20:19-21). In addition, priests were forbidden to marry prostitutes and divorced women (Lev. 21:7, 13-15). Daughters who inherited their father’s possessions had to marry within their tribe or lose their inheritance (Num. 27:8; 36:2-4).
After generations of consanguineous marriages, the Mosaic Law is rather specific in Leviticus. 18:6-18. The subject begins with the words, “None of you shall approach to any that is near of kin to him, to uncover their nakedness: I am the Lord.” There can be no doubt from this statement about who is now forbidden to marry. If there were any doubt about who is “near of kin,” we are told plainly that not only is a step-mother but also a daughter-in-law (neither of whom are actually blood kin) considered to be “near of kin” in Leviticus 20:11-12. By inspiration, Moses commanded the people not to take sisters, aunts, uncles or anyone related through marriage (in-laws) in Lev. 20:17, 19-21. Later, Moses gives one exception to this command in the Levirate Marriage laws.
The book of Deuteronomy (Deut. 22:30) also emphasized that a man may not take his father’s wife (neither his birth mother nor his step mother). A reference to this is law is seen in 1 Corinthians 5:1, where Paul says, “…such fornication as is not so much as named among the Gentiles, that one should have his father’s wife.” We see another graphic example of how God views this practice in Deuteronomy 27:20-23. Several comparisons show just how hideous these crimes really are. As the land of Canaan was being divided among the tribes, the writer states that the tribe of Ruben will not inherit because of Ruben’s sin against “his father’s bed” (1 Chr. 5:1). Keep in mind Bilhah was Jacob’s concubine but not Ruben’s birth mother (Gen. 35:22; Gen. 49:4). Then through the prophet Ezekiel, we read more of how the Lord viewed Israel’s terrible sins. They not only defiled their father’s beds, but uncovered the nakedness of menstruous women or even their own sisters—more of the horrors of incest (Eze. 22:11).
WAS THERE AN EXCEPTION TO THIS RULE?
What if the young Hebrew wife lost her husband by war or accident? What would happen to her? She was suppose to remain within her husband’s clan and wed his brother or nearest of kin. This arrangement is the exception (Lev. 20:17, 19-21) known as LEVIRATE MARRIAGE (when a brother was required to marry his brother’s widow). This law is the basis for the account of Ruth and Boaz (Deut. 25:5-10; Ruth 3:13; 4:1-12).
Yet another example of this practice is seen in the life of Judah and his daughter-in-law, Tamar (Gen. 38:6-31). Tamar’s husband was wicked and God slew him; therefore, another son was supposed to be given to her. When the second son also died because of his wickedness in refusing to give Tamar seed to conceive a child, Judah refused to give her his youngest for fear he also might also die. At this point Tamar took it upon herself to force Judah to give her a husband.
Judging from the arguments the Sadducees used against Jesus’ teaching about the resurrection of the dead, one can see that the Levirate marriage law was still in force during the life of Christ (Matt. 22:23-28; Mark 12:19-23; Luke 20:27-33).