"So, because you are lukewarm, and neither hot nor cold, I will vomit you out of my mouth."
"Hot or cold please; not lukewarm, or I'll spit you out." (more informal)
"Be hot or cold, not lukewarm, or I'll vomit you." (shorter)
Parallel translations (many different versions):http://bible.cc/revelation/3-16.htm
Please note that most of the texts in the Bible have been passed from mouth to mouth over a long period of time before being written, and were translated to many languages.