The words Jesus said are spirit and they are life

John 6:60-65
6:37All that the Father gives me will come to me. v65 I told you that no one can come to me unless the Father has enabled him.
Many of his disipes 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? What if you see the Son of Man ascend to where he was before! The spirit gives life; the flesh counts for nothing. The word I have spoken to you are spirit and they are life."
Jesus knows which disciples did not believe and who would betray him.
Why?
Jesus's teaching and his words are not everyone can accept, except who has been enabled by the Lord. So all of us are the mercy of God comes upon us.
Hard teaching is teaching material could not be understood to the students. Sometime is the teaching method of the teacher, sometime is the problem of the mind and heart of the students.
Flesh will perish, but the life is comes from the spirit. Flesh is temporary, but the spirit is forever.
How?
When I can not understand the words of God teaching, I should pray to the Lord to give me the word and open my spirit to know it.