William Burkitt on Luke 18:31

We find our blessed Saviour very frequently acquainting his disciples with his approaching sufferings, to prevent the offence that they might take at them, when the providence of God brought them on: this design was to arm them with expectation of his sufferings; and to quicken them to preparation for their own; yet, it is here said, That the disciples understood none of these sayings: Why so? Were not the words easy enough to be understood? Yes, but they could not reconcile them to the notion of the Messiah which they had drank in: they concluded he should be a temporal prince, and subdue their temporal enemies: but could not conceive how he, that should redeem Israel, should die, and be thus barbarously used. We have great need to consider will what notions we have concerning the things of God, before we entertain them; for false notions once taken up, are not without great difficulty laid down.