God forgives those who approach Him in earnest repentance. This includes recognizing one's sin, being penitent about it and committing one's self not to repeat the offense. The individual must know and not lose hope that God Almighty is the Eternally Merciful, Infinitely Compassionate and will be there whoever calls out to Him. While we should not despair we should realize how grave our sins are; fornication, is extremely grievous. With that in mind, forgiveness between people is an essential element of the believer. It may be one of the most difficult acts we can commit but if we find a way, God willing, it will soothe the soul. The hatred and anger should be released and any ill will should subside. As the person that forgives, this is another building block toward a constructive life and one that brings him/her closer to God. In fact, forgiveness is an act of worship and we should not miss the opportunity to do it when the time presents itself. Keeping the above in mind, the husband merely has to find it in himself to forgive his wife. There is no ritual or words or actions; simply, forgive. Hopefully, they will discuss it and rectify the matter and reconcile without the issue haunting their marriage. After all, it is forgiveness. Even if he will never forget and it may play on his mind once he forgives he must find that inner peace that will allow him to heal those wounds. May God be with you, the husband and the wife and their family and may He help them through their marriage. I hope this helps. God knows best. Answer published by Ronnie Hassan