20 Let each of you remain in the condition in which you were called. 21 Were you a slave when called? Do not be concerned about it. Even if you can gain your freedom, make use of your present condition now more than ever.[c] 22 For whoever was called in the Lord as a slave is a freed person belonging to the Lord, just as whoever was free when called is a slave of Christ.
S. Scott Bartchy outlines the varying interpretations of this text, using two ‘readings’ of the text: scholars, translations and theologians who favor “take freedom” and those who favor “use [or stay in] slavery.” For those who accepted the first category “take freedom,” we have Origen of Alexandria, Ephraem and Syrus, Jerome, the opponents of Chrysostom, Erasmus, Luther, Calvin, C. Hodge, Lightfoot, C.H. Dodd, the RSV, C.F.D. Moule, NEB and TEV. Modern commentators include Gordon D. Fee, Philip Payne, Robert A. J. Gagnon and Alan F. Johnson.
For those who prefer the “use [stay in] slavery” opinion, we have Chrysostom, Ambrosiaster, Cyril of Alexandria, Pelagius, John of Damascus, Sedulius Scotus, Peter Lombard, Thomas Aquinas, Bengal, Jonathan Edwards, Von Harnack, Goodspeed, Dietrich Bonhoeffer, Kummel, Kasemann and Barrett.
So, the question comes to this: did Paul call for slaves to attain freedom, or to stay as a slave? The bigger historical question is could a slave refuse manumission (freedom)? Most plausibly, he/she couldn’t. Reasons for manumission are complex, but usually derived from the generosity or personal interest of the owner. Social “generosity” included egoism and narcissism, but one doubts that a freed slave would care much for the reasons of manumission. In regards to the slave’s options regarding their freedom, “Under both Greek and Roman law, a person in slavery could seek to bring nearer the day of his manumission by working hard and by conducting himself in a manner which pleased his owner.” Financially, one could buy their manumission, as a slave once bragged “he paid 50,000 sesterces for his freedom.” Most probably, since slaves were within the poverty line, hard labor and the good nature of their owner was their most likely method of freedom. The nature of Mark 10:45 “ransom for many” evocates the language not only of liberation from slavery (physical) but also that this is something that the Messiah sought to fulfill. To fulfill this, to some early Christians, was to be “in Christ.”
In short, it is historically implausible that a slave (still beneath his or her master) could refuse his manumission from the owner that still owns him. Since there is no evidence for this, the nature of “but if you are actually able to be free, take advantage of the opportunity” (CEB) is clear: do not be bothered if you are ‘called into Christ’ when you are in slavery. But since you cannot remain a slave when manumitted, ‘do not become [or stay] as a slave to people.’ Paul’s awareness of the historical nature of manumission (as well as his Judaism) supports the reading of “take freedom” since a slave simply didn’t have any alternative.
Bartchy notes that “as a first century Jew from Tarsus who had spent much time in Jerusalem, Paul was well-acquainted with the enslavement of both Jews and Gentiles…” Paul was most likely not unsurprised by the institution of slavery, but was aware of the tension displayed in Galatians 3:28 as well as the fundamental equality for every human being. Since the shift of the eschatological age, Paul was clearly not comfortable with slavery. As Gagnon suggests, “…1 Cor. 7:21 should be read as Paul’s attempts to support freedom from slavery as at least penultimate good.” Slavery was a given in the ancient world, and it must be said that Paul wasn’t on a campaign to end the institution. However, since manumission was not an isolated occurrence in the first century, many slaves ‘in Christ’ could attain their freedom and be brought out of slavery [both physical and spiritual] to serve Christ; and Paul most certainly wouldn’t prevent them from fulfilling their “status of being the Lord’s free person” (CEB).
 S. Scott Bartchy, MALLON CHRESAI: First Century Slavery & 1 Corinthians 7:21, 6-7.
 The list apparently surprised Gordon D. Fee who calls the findings “impressive!” 1 Corinthians, 316 n41. In the following list, Bartchy’s opinion is of course the former reading.
 Who twisted the text to mean, “Go free from marriage.”
 Both who took it to mean, “go free to preach.” While arguably as convincing as Origen’s reading, this does display some hope that slaves could indeed be ‘preachers.’
 He read it as free “from marriage.”
 Unnamed as Chrysostom doesn’t give them (and us) the benefit of any recognition.
 Gordon D. Fee, 1 Corinthians, 317-320.
 Philip Payne, Man and Woman, One in Christ, 91.
 Robert A. J. Gagnon, The Bible and Homosexual Practice, 446-47. See especially n171.
 Alan F. Johnson, 1 Corinthians, 121-123.
 Who argues against the unnamed opponents in n359.
 Who took it as “stay in marriage,” a reading that suggests matrimony was anything but a picnic in those days.
 As opposed to Civil War slavery, the system wasn’t entirely predicated upon the skin color of the slave.
 “An owner usually based good treatment of slaves on the desire to gain a reputation for generosity rather than on insight into a slave’s inherent equality as a human being.” S. Scott Bartchy, “Slaves and Slavery in the Roman World,” The World of the New Testament, 176.
 S. Scott Bartchy, MALLON CHRESAI: First Century Slavery & 1 Corinthians 7:21, 97.
 Marleen B. Flory, “Family and Familia’: A Study of Social Relations in Slavery” Ph.D dissertation 1975, Yale. 112.
 S. Scott Bartchy, MALLON CHRESAI: First Century Slavery & 1 Corinthians 7:21, 116.
 Paul’s consistent use of ‘slave language’ to describe himself and others attests to this point. We were once “slaves of sin” (Rom 6:16-20); Paul has “made himself a slave to all…” (1 Cor. 9:19); “slaves for Jesus’ sake” (2 Cor. 11:20); “no longer a slave, but a child, and if a child then also an heir, through God” (Gal. 4:7); “become slaves to one another” (Gal 5:13) and ultimately, Paul says this of Christ who “took the form of a slave” (Phil 2:7).
 Robert A. J. Gagnon, The Bible and Homosexual Practice, 444. While he disagrees with some of Bartchy’s translational work, he supports the overall thesis.