In the New Testament the Greek word porneia (from porne, a prostitute) was used for both prostitution and sleeping around. Such behaviour used to be called fornication, a word which is still used by some preachers. We prefer to translate it in modern idiom as promiscuity, or sex without love, commitment, or psychological intimacy. No family table is established, and there is no intention to continue the relationship beyond the immediate sexual satisfaction that the occasion affords.
In our mind whereas adultery is unfaithfulness to a marriage commitment, porneia accepts no commitment. We have seen how it was viewed as a matter of indifference in Old Testament patriarchy, and it is not considered immoral even for married men in modern Arabia. We then wonder why porneia or sleeping around suddenly began to be viewed with such abhorrence by the early Christians?
Our conclusion is that porneia was a way of using the body of another without any love for the person. It was therefore a denial of agape, or God's kind of love. Paul argues that since our bodies are to be instruments for Christ's loving, we should not use our body for such unloving purposes. "The body is not meant for fornication but for the Lord, and the Lord for the body." It seems that for Paul porneia is a misuse of sex, which is designed by God for uniting a couple in a loving marriage. [1 Corinthians 6:13-15]
Paul then goes on to explain that union with a prostitute sets up a rudimentary marriage which is then immediately aborted. "Do you not know that whoever is united to a prostitute becomes one body with her?" And he quotes the original definition of marriage from the second chapter of the Bible. "The two shall become one flesh" [1 Corinthians 6:16-17] What is wrong with promiscuity or prostitution is not that the couple engage in sex without being properly married. In Paul's terminology they are in a sense married and divorced within the hour.
The apostle adds that in contrast to porneia sex should result in the couple together forming a temple of the Holy Spirit, and the first fruit of the Holy Spirit is love. [1 Corinthians 6:19 compared with Galatians 5:22] Our impression is that anyone who keeps using sex for merely physical gratification is going to find it very hard to engage in a marriage where sex is the outward and visible sign of a long term commitment to the love we have outlined in Chapter 1 and Chapter 2.