John 16:18
So they kept saying, "What does He mean by saying, 'a little while'? We do not know what He is talking about."
Matthew 16:9-11
Do you not understand yet? Do you not remember the five loaves for the five thousand and how many basketfuls you took up?
Luke 24:25
Then He said to them, "O men sluggish in mind and slow in heart to believe all that the prophets have said!
Hebrews 5:12
For although you ought to be teachers of others because you have been Christians so long, you actually need someone to teach you over and over again the very elements of the truths that God has given us, and you have gotten into such a state that you are in constant need of milk instead of solid food.