דברים, פרק כ״ד, פסוק ד׳

Marriage is a sacred institution, and its dissolution followed by a new union creates an absolute, irreversible boundary. If a man divorces his wife and she subsequently marries another man, the original couple is permanently forbidden from remarrying, regardless of whether the woman's second marriage ends in divorce or widowhood [ביאור שטיינזלץ]. This strict prohibition applies even if the second relationship only reached the stage of formal engagement [מזרחי, הכתב והקבלה, תורה תמימה]. Interestingly, this boundary is strictly tied to the formalization of a new relationship; if the divorced woman never marries another but engages in promiscuity, she remains permitted to return to her first husband [שד״ל, העמק דבר, תורה תמימה].

The rationale for this permanent separation is that the woman is considered defiled. This raises a natural question, as her second marriage was entirely legal and permitted. The primary approach among commentators is that this does not imply an objective moral failing or sin. Rather, it is a relative state of impurity; she is considered defiled and forbidden exclusively in relation to her first husband, simply because she shared intimacy with another man [אבן עזרא, רמב״ן, רבנו בחיי, רש״ר הירש, ברכת אשר]. The unique phrasing used to describe this defilement suggests a blend of actual and conceptual impurity. In some cases, the defilement is literal, such as an act of adultery committed willingly or under coercion. In the context of a legal second marriage, however, the defilement is conceptual—while the woman bears no moral flaw, divine decree establishes that she is legally considered impure regarding her first husband [הכתב והקבלה, רש״ר הירש, ביאור יש״ר]. Furthermore, the Sages derive from this language an additional warning against a married woman who commits adultery, explicitly reinforcing that she becomes permanently forbidden to her husband [רש״י, רמב״ן, מזרחי, רבנו בחיי, שפתי חכמים, גור אריה].

Reestablishing the original marriage after a second union is described as an abomination before God. The underlying purpose of this severe designation is to prevent legalized promiscuity and wife-swapping. Without such a restriction, men might temporarily divorce their wives, pass them to friends, and later remarry them, effectively using the sacred institutions of marriage and divorce as a legal cover for adultery [ספורנו, רמב״ן, שד״ל, רלב״ג, בכור שור, ביאור שטיינזלץ]. The prohibition specifically targets the formal act of remarrying her through official betrothal and marital relations [העמק דבר, תורה תמימה]. Yet, while the remarriage itself is an abomination, any children born from such a forbidden union bear no stigma; they are entirely legitimate members of the community [תורה תמימה].

Ultimately, these laws serve to protect the moral fabric of the land. Behaviors akin to wife-swapping and institutionalized promiscuity corrupt society, invite severe transgressions, and actively damage the physical blessings and agricultural yield of the land [העמק דבר, אם למקרא]. Consequently, the responsibility to uphold these standards extends beyond the individual. It is a direct mandate for the courts and the justice system to actively guard family purity, prevent the exploitation of marital laws, and ensure the moral integrity of society [רמב״ן, הטור הארוך, רש״ר הירש, ביאור יש״ר, תורה תמימה].