Contradiction with Mark 9:32
Mark 9:32 states that the disciples did not understand Jesus’ saying, similar to Luke 9:45, but adds they were afraid to ask him, implying their fear rather than divine concealment which contradicts the notion of intentional concealment by God.
Mark 9:32: But they understood not that saying, and were afraid to ask him.
Contradiction with John 16:25
Jesus tells his disciples that he will speak plainly of the Father, contradicting the idea in Luke 9:45 that the meaning was hidden from them.
John 16:25: These things have I spoken unto you in proverbs: but the time cometh, when I shall no more speak unto you in proverbs, but I shall shew you plainly of the Father. [proverbs: or, parables]
Contradiction with Matthew 13:11
Jesus explains that it is given to the disciples to know the mysteries of the kingdom of heaven, contradicting the hidden understanding in Luke 9:45.
Matthew 13:11: He answered and said unto them, Because it is given unto you to know the mysteries of the kingdom of heaven, but to them it is not given.
Contradiction with 2 Corinthians 3:14-16
Paul writes about the veil being taken away when one turns to the Lord, contrasting with the idea of understanding being intentionally hidden in Luke 9:45.
2 Corinthians 3:14-16: But their minds were blinded: for until this day remaineth the same vail untaken away in the reading of the old testament; which [vail] is done away in Christ.