Having confidence in thy obedience I wrote unto thee, knowing that thou wilt also do more than I say. Having confidence in thy obedience - to my apostolic authority, were I to "enjoin" it (Philemon 1:8), which I do not, preferring to beseech thee for it as a favour (Philemon 1:9).
Thou wilt also do more - toward Onesimus: hinting at his possible manumission, besides being kindly received.