Philemon 6 (ESV) … “and I pray that the sharing of your faith may become effective for the full knowledge of every good thing that is in us for the sake of Christ.”
That the sharing of thy faith may become effectual.…
The word translated “sharing” here can better be rendered “fellowship.” Handley Moule suggests that the word, as used here, refers to Philemon’s generous financial fellowship prompted by the dear brother’s love for the Lord Jesus. Perhaps Paul himself had profited from Philemon’s generosity. One way that Philemon translated his faith and love into action was by sharing his material wealth with others.
This was no doubt a noble and commendable thing to do; but, ordinarily, human love can prompt mere philanthropy. Many a successful, unsaved businessman has been generous with his money. Many charities are made possible through such men. Moreover, generous giving to the Lord’s work and God’s people does not in itself necessarily denote a vital state of soul. Paul does not want Philemon to show kindness and charity to Onesimus on merely human grounds. So he goes on.
 Phillips, J. (2009). Exploring Colossians & Philemon: An Expository Commentary (Phm 6a). Kregel Publications; WORDsearch Corp.