Samuel grew, and Yahweh was with him, and did let none of his words fall to the ground.
"The Lord ... let none of his words fall to the ground"  (1 Samuel 3:19).  The undeniable proof of the validity of God's inspiration of his prophets lay in the fact that what they prophesied came to pass, exactly as foretold.  The reality of the countless "predictive prophecies" of the O.T. is the mountain truth which all the unbelievers of the ages have never been able to remove.