Sheikh Muhammad Nur Abdullah, president of the Islamic Society of North America (ISNA) and member of the Fiqh Council of North America, states the following: The Prophet (peace and blessings be upon him) is reported to have said: “Allah has set certain limits, so do not violate them.” In another hadith he is reported to have said: “Whoever committed any of these abominable acts but was covered by Allah, let him or her not expose what Allah has covered.”

In general, someone should not speak about what Allah has covered, especially after he or she has repented. Hence, if a wife admits to her husband about a previous sin, it shows that she is honest and repenting. It is also a good sign that her husband forgave her.
Now, with regard to applying the punishment, it is not required for the husband to apply the Shari`ah penalty on her. The Shari`ah penalties are not to be applied by individuals; there is a process that has to followed, going to the legal system, and making sure that the four witnesses are provided. The penalty is to be applied by a Muslim judge who gives a court decree for the application of the punishment. Since this is not available, then she has to repent to Allah, ask for forgiveness, and increase her good deeds so that Allah will remove her sins.