John 6:60-66 — Many therefore of His disciples, when they had heard this, said, This is an hard saying; who can hear it?
When Jesus knew in Himself that His disciples murmured at it, He said unto them, Doth this offend you?
What and if ye shall see the Son of man ascend up where He was before?
It is the spirit that quickeneth; the flesh profiteth nothing: the words that I speak unto you, they are spirit, and they are life.
But there are some of you that believe not. For Jesus knew from the beginning who they were that believed not, and who should betray Him.
And He said, Therefore said I unto you, that no man can come unto Me, except it were given unto him of my Father.
From that time many of His disciples went back, and walked no more with Him.
His disciples (verse 60) — not the 12. Others, probably, who followed Jesus hoping He would establish the kingdom as in John 2:23-25.
Verse 62 — referring to His ascension after the resurrection.
Spirit — Holy Spirit. He gives spiritual life through the words Christ speaks.
When men resist the truth, Jesus makes it even harder to understand. In essence, you think it's hard to grasp that I came as a man (verse 41) and will die as a man (verse 52, 55)? What will you say when I ascend to heaven as a man? (verse 62). Would they believe then? No (verse 64).
All may come if they will, but none would come apart from the drawing of the Father. (verse 65)
hard = harsh, rough
Does this offend you? = Does this cause you to stumble? Offend (skandalizo) is often used in the New Testament to indicate falling away into unbelief.
The flesh profiteth nothing — When He said "eat my flesh" He wasn't referring to His physical body.
To receive His words is to receive life.
Went back (verse 66) = went to the things behind. Their former unbelief.