And they understood none of these things: and this saying was hid from them, neither knew they the things which were spoken. – Luke 18:34

They listened to this private talk, but we are told by Luke that it was very much lost upon them, because they did not understand Him. “And they understood none of these things: and this saying was hid from them, neither knew they the things which were spoken.”…Numbers of people imagine that they understand mysteries, and yet the simplicities of the faith are hid from their eyes because they are gazing after abstruse doctrines. They search after difficult things and miss the plain truth. We groan as we wantonly dive into a profound abyss; and yet we stand confounded over a little transparent stream, which, to wade through, would bring us bliss. When our Lord told the twelve that He would die, they imagined that it was a parable, concealing some deep mystery. They looked at one another, and they tried to fathom where there was no depth, but where the truth lay on the surface. The deep things of God thousands will pry into; but yet these are not saving matters, nor are they of any great practical value. Fixed fate, free-will, predestination, prophecy, and the like, these have small bearings upon our salvation from sin; but in the death of our Lord lies the kernel of the matter. Beloved, when we try to commune with Jesus, let us wear the garments of simplicity. It is the serpent who trades in subtlety, but I would have you remember “the simplicity which is in Christ Jesus.” There is in Him a depth which we cannot fathom; but His every word is pure truth, and those things which are necessary are made so plain that he who runs may read, and he who reads may run. Believe Him to mean what He says, and take His promises as they stand, and His precepts in their plain meaning; and, oh, if we do this, we shall be made greatly wise! ~ C.H. Spurgeon

https://www.blueletterbible.org/Comm/spurgeon_charles/sermons/2212.cfm