Charles Spurgeon Commentary Philemon 1:19

"I Paul write it with mine own hand, I will repay it: that I say not unto thee that thou owest to me even thine own self besides." — Philemon 1:19 (ASV)

Paul had been the means of Philemon's conversion, so he was immeasurably in debt to the apostle; but Paul only gently reminds him of the fact as a reason why he should deal kindly with Onesimus for his sake.