Mark 4:12
that in seeing they may see and not perceive, and in hearing they may hear and not understand, least they should be converted, and their sins be forgiven them.
Mark 8:17-21
And Jesus knowing it saith unto them, What are ye reasoning about? because ye have no bread? Do ye not yet discern nor understand? have ye your heart still hardened?
Ephesians 2:11
Wherefore remember that ye were formerly Gentiles in the flesh, called uncircumcision by that which is called circumcision made by hands in the flesh;
2 Thessalonians 2:10-12
and wonders, and with all iniquitous fraud, among those that shall perish; because they received not the love of the truth, by which they might be saved.