If you have not turned aside to uncleanliness under your husband. (5:19)
The word Tachath implies two meanings; 1) "under”, 2) and “instead of.”
1) The concept of being under the authority of the husband is a foundation of marriage. A ship cannot have two captains; and although the wife must be accorded full respect (as stipulated in the Ketubah contract), the husband and father is the head of the household.
When a wife challenges the husbands authority, she thereby disrupts the structure of marriage and opens the door for rebellion against Hashem and His laws. The revolt against authority is the beginning of a spirit of revolt against decency and propriety, and eventually against Hashem.
2) “If you have not turned aside to uncleanliness instead of your husband.” The spirit of dissension causes various forms of misbehavior, including the urge to spite. In order to demonstrate liberation from authority, a wayward woman may become friendly with someone other than her husband, which may become a ruination of her life.
But another factor now enters into this disorderly situation whereby the natural rhythm of life is disrupted.
This second interpretation of Tachas as “instead” is an important explanation of the sad phenomenon of infidelity.
When a woman quarrels with her husband, she should not discontinue the routine of married life. She must perform the domestic duties without any interruption, and among these is the duty of accommodating her husband in marital relations.
When she attempts to avenge herself by denying herself to her husband, she thereby imperils not only the marriage but she brings herself to the brink of destruction.
The urge for relations with a man causes her to become wayward, and "stolen waters become sweet” (Mishle 9:17) and even the lowest and most despicable man may entice her “instead” of her husband.
But when the regular domestic routine continues, there is always the best hope for reconciliation; evil temptations are not even able to enter the mind.
The Creator has fashioned men and women in such manner that the normal conduct of matrimony continues to heal the breaches that frequently occur in human relations.