Biblical law permits voluntary slavery because it recognizes that some people are not able to maintain a position of independence. To attach themselves voluntarily to a capable man and to serve him, protected by law, is thus a legitimate way of life, although a lesser one.
Sounds like working for any company or corporation now days.
Related info on the Founders (if you get error message “No such file (give_legacy_article)” press F5 several times to get the article)
Was the American Founding Unjust? (The Case of Slavery)
1) http://www.freerepublic.com/forum/a377e2d151100.htm
2) http://www.freerepublic.com/forum/a377e2f80122d.htm
I don't recall any reference to the Bible in in the Constitution, can you identify specifics?