John 6:60
Therefore, many of his disciples, when they heard him, said: This is a hard saying; who can hear it?
John 6:66
After this, many of his disciples went back, and walked with him no more.
Matthew 11:6
and blessed is he that shall find in me no cause of offense.
John 6:41-42
Then the Jews murmured at him, because he said, I am like bread that came down from heaven.
John 8:31
Then said Jesus to those Jews that believed on him: If you continue in my word, you are my disciples indeed,
John 8:43
Why do you not know what I say? Because you can not understand my words.
Hebrews 5:11
Of him we have many things to say, and difficult to be explained, if we do say them, since you are slow in understanding.
2 Peter 3:16
as also in all his letters, speaking in them of these things, in which are some things hard to be understood, which the unlearned and unstable wrest, as they do also the other scriptures, to their own destruction.