Jesus disclosed His glorious sufficiency when He said "I AM the Bread of Life." He showed the Jewish people through the miracle of Feeding the Five Thousand that He was the one who was the Bread of Life, that is, He gives True Life. But the reality of Jewish unbelief is staggering in the face of so much glory. There is a particular warning here for "religious people", in that the ones who were the most "religious" of that day were the ones who missed the Messiah, even after seeing His glory with their own eyes and tasting the miracle with their own mouths. Recall in Chapter 2 of John's Gospel that the crowds had a superficial, surface-level belief in Him, yet they weren't born again, even after having an experience of His glory. This is a very important warning for Evangelicals of today, because there's an idea that if one has a moving experience, he is saved, and his salvation shouldn't be questioned. It's the very real possibility of being around the things of God and seeing His power, and not being saved. What a horrible thing it is to be within a hand's reach of Bread and not to receive it.