Matthew 13:13-14, 35

Therefore I speak to them in parables; because while seeing they do not see, and while hearing they do not hear, nor do they understand. In their case the prophecy of Isaiah is being fulfilled, which says, ‘YOU WILL KEEP ON HEARING, BUT WILL NOT UNDERSTAND; YOU WILL KEEP ON SEEING, BUT WILL NOT PERCEIVE

This was to fulfill what was spoken through the prophet: “I WILL OPEN MY MOUTH IN PARABLES; I WILL UTTER THINGS HIDDEN SINCE THE FOUNDATION OF THE WORLD.”