Philemon 1:15
For perhaps he was therefore separated from you for a while, that you would have him forever,
WEB
For perhaps he therefore departed for a season, that thou shouldest receive him for ever;
KJV
What Philemon 1:15 means
Paul urges Philemon to take back Onesimus, a slave who had left him, and to receive him now as a beloved brother in the faith rather than punish him.
Paul wrote this short letter from prison to Philemon, a well-off Christian who hosted a church in his home. One of Philemon's slaves, Onesimus, had left him, apparently owing him something, and had since met Paul and become a follower of Jesus. Paul is sending him back, carrying this letter.
Here Paul reframes the whole situation. Perhaps, he suggests, the two were parted for a while so that Philemon could have Onesimus back for good, on entirely new terms. Roman law let an owner punish a runaway slave harshly. Paul asks for the opposite: receive him like family, as a beloved brother, the way you would receive me. He even offers to cover whatever the man owes. Without staging a debate about slavery itself, the letter quietly places the bond of shared faith above the bond of owner and owned.