With the help of Silas, whom I regard as a faithful brother, I have written to you briefly, encouraging you and testifying that this is the true grace of God. Stand fast in it. (NIV)
By Silvanus, a true (loyal, consistent, incorruptible) brother, as I consider him, I have written briefly to you, to counsel and urge and stimulate [you] and to declare [to you] that this is the true [account of the] grace (the undeserved favor) of God. Be steadfast and persevere in it. (AMP)
By Silvanus, a faithful brother unto you, as I suppose, I have written briefly, exhorting, and testifying that this is the true grace of God wherein ye stand. (KJV)