All belief in Jesus is not saving belief
23 Now when He was in Jerusalem at the Passover, during the feast, many believed in His name, observing His signs which He was doing.
24 But Jesus, on His part, was not entrusting Himself to them, for He knew all men,
25 and because He did not need anyone to testify concerning man, for He Himself knew what was in man.
New American Standard Bible: 1995 Update. 1995. La Habra, CA: The Lockman Foundation.