John 6:60-66 NIV
On hearing it, many of his disciples said, “This is a hard teaching. Who can accept it?”
Aware that his disciples were grumbling about this, Jesus said to them, “Does this offend you? Then what if you see the Son of Man ascend to where he was before! The Spirit gives life; the flesh counts for nothing. The words I have spoken to you—they are full of the Spirit and life. Yet there are some of you who do not believe.” For Jesus had known from the beginning which of them did not believe and who would betray him. He went on to say, “This is why I told you that no one can come to me unless the Father has enabled them.”
From this time many of his disciples turned back and no longer followed him.
NIV: New International Version