All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
The matter is as we have stated in the previous Fatwa that a woman should conceal herself if she had committed adultery and should not inform her husband, or anybody else about it. Informing someone else could lead to the opposite of the reasons why Sharee'ah has legislated concealing one's sins, such as spreading affection and maintaining good marital relationships between the spouses. There is no contradiction between realising the benefit of concealing one's sins and the benefit of safeguarding the rights of the husband. The wife can conceal her sin and ask her husband to forgive her without mentioning what had happened. It is good to choose the time when he would not doubt about anything for instance when failing to fulfil one small household duty and tell him that human beings usually make mistakes, and ask him to forgive her about any shortcomings or negligence that she might have done in his regard. There is no doubt that the harm of informing the husband about it, on top of violating the rule of concealing one's sins, is greater than the harm of not informing him. One of the common rules is that the least harm should be committed in order to avoid a greater harm.
Allaah knows best.