Grumbling is the outward expression of unbelief! The Jews, to whom Jesus spoke, grumbled at His words that He was (IS!) "...The Bread of Life that came down out of heaven." Again, Jesus will not, cannot fail, in saving His people...the unbelief of the Jews is no indictment on the truthfulness of Who Jesus Christ is! Be not shaken! For, "No one can come to Me" says Jesus, "unless the Father who sent Me draws him; and I will raise him up on the last day" (John 6:44)