John 10:6
Jesus told them this parable [i.e., a brief story to illustrate his teaching] but they did not understand what it meant.
Matthew 13:13-14
Therefore, I am speaking to them with parables because [although] they can see, they [really] do not perceive, and [although] they can hear, they [really] do not comprehend, and so they [utterly] fail to understand [what I am trying to get across].
Matthew 13:51
"Have you understood all these things?" [Jesus asked]. "Yes," they said to Him.
John 6:52
Then the Jews [who were assembled in the synagogue. See verse 59] began arguing bitterly with one another, saying, "How can this man give us his physical body to eat?"
John 6:60
So, when they heard [these things], many of Jesus' disciples said, "This is difficult teaching. Who can listen to it [i.e., and accept it]?"
John 7:36
What did he mean by saying, 'You people will be looking for me, but will not find me; and you will not be able to go where I will be?'"
John 8:27
The people [who heard this] did not understand that Jesus was speaking to them about the Father.
John 8:43
Why do you people not understand what I am saying? It is because you cannot [bear to] listen to my message.
John 16:25
"I have spoken these things to you in figurative language. [However], the time will come when I will not speak to you in figurative language, but will tell you plainly about the Father.
1 Corinthians 2:14
Now the natural person [Note: Since this person is contrasted with the spiritual person of verse 15, it is taken here to mean the person without the Holy Spirit] does not receive the things [i.e., truths] revealed by the Holy Spirit of God, because they are [considered] foolishness to him. And he cannot understand them because they must be discerned by using spiritual judgment [i.e., judgment aided by the Holy Spirit].
1 John 5:20
And [in addition], we know that the Son of God has come [in a physical body, See 4:2] and has given us understanding, so that we can know the True One [i.e., God], and that we are in [fellowship with] the True One, even His Son Jesus Christ. This Son is the true God and eternal life.