A.T. Robertson Commentary Philemon 1:16

"no longer as a servant, but more than a servant, a brother beloved, specially to me, but how much rather to thee, both in the flesh and in the Lord." — Philemon 1:16 (ASV)

No longer as a servant (ουκετ ως δουλον). "No longer as a slave." So it has to be here. So it should be always. Paul sends Onesimus, the converted runaway slave, back to his legal master, but shows that he expects Philemon the Christian to treat Onesimus as a brother in Christ, not as a slave.

But more than a servant (αλλ' υπερ δουλον). "But beyond a slave."

A brother beloved (αδελφον αγαπητον). A brother in Christ.

How much rather to thee (ποσω δε μαλλον σο). "By how much more to thee," because of Philemon's legal ownership of this now Christian slave. "In the flesh Philemon had the brother for a slave; in the Lord he had the slave for a brother" (Meyer).