Extramarital sex occurs when a married person engages in sexual activity with someone other than their marriage partner, this would also be known as infidelity or audltary which had the consequence of being stonned to death in the times of Jesus " If a man commits adultery with another man's wife-with the wife of his neighbour-both the adulterer and the adulteress must be put to death. (Leviticus 20:10). The negative association with sex outside of marriage arises due to the many consequences it could have; such as the 'broken trust' that follows due to the violation of the vows taken infront of God. With infidelity that has been committed by the women brings uncertanity on who the father is of any offsprings this is frowned upon as men do not want to spend money and time on children that are not theirs. Also sex outside of marriage can also spread disease to the innocent which could cause physical and emotional pain.
Utilitarianism only asks whether sexual behaviour will cause harm or give pleasure: if, on balance, it produces more pleasure than harm, then it's good. This isn't an excuse for wholesale rape and promiscuity; you have to think of your own pleasure, but also your partner's and everybody else who would be affected. This is known as the harm principle and it rules out rape, adultery in most cases and other harmful, coercive or deceitful sexual behaviours. Jeremy Bentham's writings on the law of marriage are firmly based on the principle of utility, the ‘greatest happiness principle’, which asserts that all human actions are motivated by a wish to avoid pain and gain pleasure. Bentham placed sexual love, which he described as physical desire, in the category of ‘self-regarding’ motives for human behaviour, along with ‘pecuniary interest’, love of power, and self preservation. Therefore in the course of drafting a utilitarian law of marriage Bentham set out an explanation of the pleasures and