The salutation of Paul with mine own hand; - See the notes, 1 Corinthians 16:21. “Which is the token in every epistle.” Greek: “sign.” That is, this signature is a sign or proof of the genuineness of the epistle; compare the notes on Galatians 6:11.
So I write - Referring, probably, to some mark or method which Paul had of signing his name, which was well known, and which would easily be recognized by them.