John 3:4
Nicodemus said to Him, "How can a man be born [again] after he is [already] old? He cannot enter his mother's womb a second time and be born, can he?"
John 3:3
Jesus said to him, "Truly, truly, I tell you, a person cannot see the kingdom of God [i.e., enter it. See verse 5], unless he is born from above [Note: The words "from above" are also used in verse 31, but in this place they could also mean "again," or "anew" and refer to the source of a person's second birth].
John 4:11-12
The woman [then] said to Him, "Sir, you do not have anything to draw [water] with, and the well is deep. Where will you get that living water?
John 6:53
So, Jesus answered them, "Truly, truly, I tell you, unless you eat the physical body of the Son of man and drink His blood, you do not have [spiritual] life in yourselves [Note: The references to "body" and "blood" throughout this section allude to taking Jesus' life and teaching into one's heart. See verse 56].
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]?"
1 Corinthians 1:18
For the message of [Christ dying on] the cross is foolishness to those who are perishing [i.e., in a lost state], but it is God's power to us who are being saved.
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].