John 3:4

3:4 Nicodemus saith unto him, How can a man be born when he is old? can he enter the second time into his mother’s womb, and be born?

John 3:9

3:9 Nicodemus answered and said unto him, How can these things be?

John 6:41

6:41 The Jews then murmured at him, because he said, I am the bread which came down from heaven.

John 6:52

6:52 The Jews therefore strove among themselves, saying, How can this man give us [his] flesh to eat?

John 6:60

6:60 Many therefore of his disciples, when they had heard [this], said, This is an hard saying; who can hear it?

John 12:34

12:34 The people answered him, We have heard out of the law that Christ abideth for ever: and how sayest thou, The Son of man must be lifted up? who is this Son of man?

John 16:17-18

16:17 Then said [some] of his disciples among themselves, What is this that he saith unto us, A little while, and ye shall not see me: and again, a little while, and ye shall see me: and, Because I go to the Father? 16:18 They said therefore, What is this that he saith, A little while? we cannot tell what he saith.