Do Not Commit Immoral Sexual Acts
G-d created firstly the man and the woman as one unit, and then divided them to two separate entities, which are in need of each other in order to reach completeness. Married life and its laws are, therefore, the basis for the existence of mankind and the completeness of the family and community. This comes into expression also in keeping values of modesty and discreetness in matters of marital relationship.
The practical implication of this commandment
The prohibition of incest and adultery. This includes the prohibition of sexual relationship between relatives of first degree, between a married woman and another man, between two males or with animals.
A Slightly Deeper Look
The Bible states “It is not good for man to be alone,” so G-d made a helpmate for Adam, and in marriage “He blessed them.”
In a wholesome family, man’s creativity finds meaningful expression. Wholesome families are the cornerstone of healthy communities, nations, and societies. Nations which have condoned immorality – adultery, homosexuality, sodomy, incest – have never lasted long. Sexual immorality is the sign of an inner decay which spawns a ruthless society, bringing confusion into G-d’s life plan.