The Forbidden Relationship

A relationship to someone else whose married still exist is forbidden, this is how the law of matrimony rules especially in Christian community. But this law sometimes ignored by both people who really in-love together...who met and fall in-love in a wrong dimension.

Accordingly, to fall in-love and have had a relationship to someone else aside from legal husband and wife relationship is not allowed by the law of matrimony and to the law of God. Basically it is called adultery which is written against the law of man, it is a sins in the eyes of many people, but why it is a sins and against the law if you both love each other? Is it because there are no legal papers to show to the world that they both mutually inlove? Does legal paper signifies the holiness of the matrimony of marriage? or it is a common beliefs that it is an adultery commited by both of the two who fall inlove in a wrong place and in the wrong time?