The duty of a brother-in-law, often referred to as "levirate marriage," is a biblical concept primarily found in the Old Testament. This duty is rooted in the cultural and legal practices of ancient Israel and is outlined in the Mosaic Law. The primary purpose of this duty was to preserve the family lineage and provide for the widow of a deceased brother.

Biblical Foundation

The principal passage concerning the duty of a brother-in-law is found in Deuteronomy 25:5-10. According to the Berean Standard Bible , the text states:

"If brothers dwell together and one of them dies without having a son, the widow must not marry outside the family. Her husband’s brother is to take her as his wife and fulfill the duty of a brother-in-law for her. The first son she bears will carry on the name of the dead brother, so that his name will not be blotted out from Israel."

This passage establishes the responsibility of the surviving brother to marry the widow and produce offspring in the name of the deceased brother. This practice ensured the continuation of the family name and inheritance within the tribe of Israel.

Cultural and Legal Context

In ancient Israelite society, family lineage and inheritance were of paramount importance. The levirate marriage served as a means to protect the widow from destitution and to maintain the deceased brother's property within the family. The duty of a brother-in-law was not merely a familial obligation but a legal requirement under the Mosaic Law.

The practice also reflects the communal nature of Israelite society, where family and tribal affiliations were central to identity and social structure. By fulfilling this duty, the brother-in-law upheld the honor and continuity of the family line.

Exceptions and Refusal

While the duty was a legal expectation, there were provisions for refusal. Deuteronomy 25:7-10 outlines the procedure if a brother-in-law chose not to marry the widow:

"But if the man does not want to marry his brother’s widow, she is to go to the elders at the city gate and declare, 'My husband’s brother refuses to preserve his brother’s name in Israel. He is not willing to perform the duty of a brother-in-law for me.' Then the elders of his city shall summon him and speak with him. If he persists and says, 'I do not want to marry her,' his brother’s widow shall go up to him in the presence of the elders, remove his sandal from his foot, spit in his face, and declare, 'This is what is done to the man who will not build up his brother’s house.' And his family name in Israel will be called 'The House of the Unsandaled.'"

This passage indicates that while the duty was obligatory, there was a formal process for declining it, albeit with social consequences. The act of removing the sandal and spitting in the face was a public shaming ritual, signifying the man's failure to uphold his familial responsibilities.

Historical Examples

The account of Ruth and Boaz provides a narrative example of the levirate principle, although it involves a kinsman-redeemer rather than a direct brother-in-law. In Ruth 4:5-10, Boaz acts as a redeemer for Ruth, the Moabite widow of Mahlon, by marrying her to preserve the family line. This account illustrates the broader application of the principle of familial duty and redemption.

Another example is found in Genesis 38, where Judah's son Onan is instructed to fulfill this duty for his deceased brother Er's widow, Tamar. Onan's refusal to produce offspring for his brother leads to divine judgment, highlighting the seriousness of this obligation.

Theological Implications

The duty of a brother-in-law underscores the biblical themes of family loyalty, social justice, and the preservation of God's covenant people. It reflects the importance of community and the responsibility individuals have toward one another within the covenant community. This duty also points to the broader biblical narrative of redemption and restoration, as seen in the lineage of Jesus Christ, who descends from the line of Ruth and Boaz.