Through Silvanus, our faithful brother, as I consider him, I have written to you briefly, exhorting, and testifying that this is the true grace of God in which you stand.
Stand ye fast therein ...  This reminds one of Paul's great charge, "Having done all, to stand."  The unanimous appeal of the apostles of Christ was for Christians to stand firmly against every foe, not being swept off their feet, or made to defect from the holy faith by anything whatsoever.