USBN National Baha’i Review #4 April 1968 p5
The Baha'i Teachings on this matter, which is of such vital concern and about which there is such a wide divergency of views, are very clear and emphatic. Briefly stated the Baha’i conception of sex is based on the belief that chastity should be strictly practiced by both sexes, not only because it is in itself highly commendable ethically, but also due to its being the only way to a happy and successful marital life. Sex relationships of any form, outside marriage, are not permissible therefore, and whoso violates this rule will not only be responsible to God, but will incur the necessary punishment from society.
"The Baha'i Faith recognizes the value of the sex impulse, but condemns its illegitimate and improper expressions such as free love, companionate marriage and others, all of which it considers positively harmful to man and to the society in which he lives. The proper use of the sex instinct is the natural right of every individual, and it is precisely for this very purpose that the institution of marriage has been established. The Baha’is do not believe in the suppression of the sex impulse but in its regulation and control.
"In the Aqdas and innumerable Tablets, most of which have not been yet translated, both Baha'u'llah and 'Abdu'l-Baha emphasize the above view and up-hold the principle of chastity. In The Gleanings there are some important references, more or less direct, to this question. You should carefully go over them, and ponder on their meanings and their far-reaching implications."
1938-09-05 to an individual re Baha’i concept of sex
While portions of this letter are cited various places, this is the most complete