Biblical Concept: New Scriptures?

The Christian Scriptures were originally written in Hebrew, Aramaic, and Koine Greek.  Various religious groups coming up with new scriptures have no manuscript tradition to back their additions.

           NAS Proverbs 30:5 Every word of God is tested; He is a
           shield to those who take refuge in Him. 6 Do not add to His
           words lest He reprove you, and you be proved a liar.
The original Scriptures are already sufficient in their spiritual content.  No additions, over 1900 years later, are needed.

               KJV 2 Timothy 3:16 All scripture is given by inspiration of God, and is
               profitable for doctrine, for reproof, for correction, for instruction in
               righteousness: 17 That the man of God may be perfect, thoroughly
               furnished unto all good works.