1 Corinthians 6:16

What? know ye not that he which is joined to an harlot is one body? for two, saith he, shall be one flesh (KJV)

Then: An understanding of union includes a definition that the two become one flesh (physical). It also believes that prostitutes are non-believers. Those two explanation detail Paul's abhorrence of Christ joining with a harlot (Fee, p. 259). Members of the Corinthian Church ought to instinctively feel the same way. If not, their committment is thoroughly shambled.

Now: For years, the Catholic church upheld a standard of its members being barred from marrying anyone but another member of the church. Protestants focused on the hope that marriage would ultimately bring the non-believer into salvation. Hays (p. 109) rightly asserts that the call to confront the culture is no less than in Paul's days. Teaching, upholding and promoting reverence for the body as God's temple calls out for a major priority of today's church

Extra source: The First Epistle to the Corinthians by Gordon D. Fee (Eerdman's 1987) online at http://books.google.com/books?id=XlBp10nUTXAC&dq=Gordon+Fee+Bible+commentator&printsec=frontcover&source=in&hl=en&ei=SwLNSu3nA4v6Mf2XlDo&sa=X&oi=book_result&ct=result&resnum=12#v=onepage&q=&f=false
First Corinthians by Richard B. Hayes (John Knox Press, 1997) on line athttp://books.google.com/books?id=M_PC0PAs3VYC&dq=1+Corinthians+and+Richard+B.+Hays&printsec=frontcover&source=in&hl=en&ei=2oPcStDCIIvf8Aaq0Ki3BQ&sa=X&oi=book_result&ct=result&resnum=11&ved=0CCMQ6AEwCg#v=onepage&q=1%20Corinthians%20and%20Richard%20B.%20Hays&f=false