In the context of biblical law and ethics, the act of a man lying with his brother's wife is addressed with specific instructions and prohibitions. This topic is primarily discussed in the Old Testament, particularly within the Levitical laws, which outline the moral and ceremonial codes for the Israelites.

Levitical Law:

The book of Leviticus provides explicit instructions regarding sexual relations and familial boundaries. Leviticus 18:16 states, "You must not have sexual relations with your brother’s wife; that would shame your brother." This verse is part of a broader section that details various prohibited sexual relationships, emphasizing the importance of maintaining family honor and purity.

Further, Leviticus 20:21 reiterates the prohibition and outlines the consequences: "If a man marries his brother’s wife, it is an act of impurity; he has dishonored his brother. They will be childless." This passage underscores the severity of the act by associating it with impurity and dishonor, and it suggests a divine consequence of childlessness for those who engage in such a relationship.

Deuteronomic Law:

The book of Deuteronomy also touches on the subject, though in a different context. Deuteronomy 25:5-10 discusses the practice of levirate marriage, where a man is encouraged to marry his deceased brother's widow to produce offspring in the brother's name. This practice is an exception to the general prohibition and serves a specific purpose of preserving the family lineage and inheritance.

New Testament Context:

In the New Testament, the issue of a man lying with his brother's wife is indirectly addressed in the account of Herod Antipas and Herodias. John the Baptist rebukes Herod for taking Herodias, his brother Philip's wife, as his own. Mark 6:18 records John's words: "For John had been telling Herod, 'It is not lawful for you to have your brother’s wife.'" This narrative highlights the continued recognition of the Levitical prohibition and the moral expectations upheld by Jewish law.

Cultural and Theological Implications:

The prohibition against a man lying with his brother's wife reflects broader themes in biblical law concerning sexual morality, family integrity, and social order. The laws serve to protect familial relationships and ensure the proper transmission of inheritance and lineage. The exception of levirate marriage illustrates the flexibility within the law to address specific social needs while maintaining the overarching principles of honor and purity.

Throughout the biblical narrative, the act of lying with a brother's wife is consistently viewed as a violation of divine law, with significant moral and social implications. The biblical texts emphasize the importance of adhering to God's commandments to maintain the sanctity of family and community life.