If this was just the first time, the husband should ask her in what area of their marital life has he failed? Why did she succumb to the temptation? Also depends on how long they have been married. And who was the man? An ex? How did they get close enough to make her give in? I need answers to these questions before I give my advice. Nevertheless, since the deed has been done, then man needs a lot of counselling because the experience can be too devastating for a faithful husband to handle.