the text says He intentionally stopped teaching clearly in public and instead spoke only in parables so that it would be fulfilled what He had commanded the prophet long ago,
"Keep on hearing, but do not understand;
Keep on seeing, but do not perceive.
Make the heart of this people dull,
And their ears heavy,
And shut their eyes;
Lest they see with their eyes,
And hear with their ears,
And understand with their heart,
And return and be healed."