We hear Paul’s letter to Philemon so infrequently—it turns up in our Sunday readings only once every three years—that it is worthwhile to pause and savor it when it appears. Perhaps more than any other New Testament document, this brief note (25 verses) helps us realize that when we read an epistle of Paul we are reading someone else’s mail. As in the case of most personal correspondence, the sender presumes much on the part of his receivers: e.g., knowledge of Paul’s location (in prison, but where?), Philemon’s venue (Colossae? Col 4:9 refers to Onesimus as “one of you”), the context of the slave’s running away (sheer desire for freedom? fear of reprisal for mismanagement on his part?). Much of what the original readers/listeners knew we can only guess at.

Other things are clear. Philemon hosts a church gathering that meets regularly at his house. Onesimus is Philemon’s slave and he has run away—a capital crime in the Roman Empire. Paul is sending him back, expecting not only reconciliation but something “more” (manumission [a slave owner freeing his or her slaves]?). Though much of the letter has the sound of a personal note, it turns out to be a very public document. Paul names Timothy along with himself as a sender of the letter, and he mentions five other imprisoned fellow Christians who know he is sending this message. And the addressees of the letter are not only the three named at the outset but “the church that meets at your house” as well—a reminder that first-century writings were typically intended to be performed orally by a reader for a group.

It is hard to imagine Paul saying to fellow prisoners Luke and Mark, “You know, guys, this is such a fine letter. I’ll bet that one day they’ll make it part of the Bible.” And yet, the letter to Philemon stands securely among the twenty-seven books of the New Testament canon. Why? Simply because St. Paul wrote it? But the New Testament is more than a reliquerium. Because Onesimus, freed for mission, eventually became the Onesimus mentioned as bishop of Ephesus fifty years later by Ignatius of Antioch? Possibly, but we don’t know for sure.

The best reason for being enshrined in the canon may well be the letter’s (implied) teaching about baptism, conversion, and Christian community. Notice the kinship language Paul uses throughout the note: Timothy is called “brother,” Philemon is “beloved,” Apphia is “our sister,” Onesimus is “my child”—“fathered” by Paul during his imprisonment (because Paul has “parented” the slave into the new life of Christian faith). For Philemon, the consequence of Onesimus’ conversion to Christ is that the runaway is no longer simply a slave but a “brother in the Lord.”

In this family language we find a dramatic and concrete expression of the principle Paul alluded to in Galatians 3:28 (“There is neither Jew nor Greek, … neither slave nor free person, … not male and female; for you are all one in Christ Jesus”). Baptism into the body of Christ has created an equality of dignity that transcends distinctions grounded in race, law, and even gender. Rather than call for the abolition of the institution of slavery—a prospect beyond the wildest imagination of a member of a small movement in a huge and powerful empire—Paul nonetheless plants a seed that, with painful slowness, came to fruition centuries later.

This sensitive and clever letter of intercession illustrates well the point of this Sunday’s Gospel. When Jesus lays down the shocking teaching that following him entails a readiness to turn one’s back on family members, he is naming a stark consequence that accompanies good news: finding and following the will of God in Jesus makes us part of a new family that goes deeper (and wider) than blood. That was a stretch for Philemon and a risk for Onesimus. It remains so for us—which is why this letter, originally “someone else’s mail,” made it into the Bible.