Men who are not wantons or immoral are bound to consider sexual intercourse justified only when it occurs in a marriage and is indulged the purpose of the begetting children, since that is lawful, unjust and unlawful when it is mere pleasure-seeking even in marriage.
(Musonius Rufus, "On Sexual Indulgence" (Fragment 12) in Moral Exhortation, A Greco-Roman Sourcebook, edited by A.J. Malherbe, Library of Early Christianity (Philadelphia Westminster, 1986. pp. 152-153) (Nakleden: p. 90 luke timothy johnson and mark d. Jordan, Sex, Marriage, and Family in World Religions Edited by Don S. Browning M. Christian Green John Witte Jr.)