3:81 God took a covenant from the prophets: "For what I have given you of the book and wisdom, then a messenger will come to you authenticating what is with you. You will acknowledge him and support him." He said, "Do you testify, and agree to this burden?" they said, "We testify." He said, "Then bear witness, and I am with you bearing witness."
How did RK authenticate existing scripture? can RK followers explain this a little bit thoroughly