This short letter was written by Paul to his slave-owner friend and fellow believer, Philemon. Paul was writing about Onesimus, who he had recently converted, and who happened to also be a runaway slave belonging to Philemon. Since Paul was in a position of authority among believers, this would have been a great opportunity for him (and God) to condemn slavery -- if he (and God) had anything against it, that is. But apparently he didn't. Instead he returned the slave to his owner without so much as a word against the institution of slavery.
The only other thing of interest in this letter is the rather strange expression, "refresh my bowels in the Lord." Okay, I know that Paul's bowel trouble is just an artifact of the King James translation. But it sounds too funny to pass up.