John Chrysostom

Whence then shall we know them, he says? For this very reason, he added, "The salutation of me Paul with mine own hand, which is the token in every Epistle: so I write. The grace of our Lord Jesus Christ be with you all." He does not here mean, that this is the token,-for it is probable that others also imitated this,-but that I write the salutation with mine own hand, as is the custom also now among us. For by the subscription the writings of those who send letters are made known.