Yesaya 6:9

6:9 He said, “Go and tell these people:

‘Listen continually, but don’t understand!

Look continually, but don’t perceive!’

Markus 4:12

4:12 so that although they look they may look but not see,

and although they hear they may hear but not understand,

so they may not repent and be forgiven.” ¹ 

[4:12]  ¹ sn A quotation from Isa 6:9-10. Thus parables both conceal or reveal depending on whether one is open to hearing what they teach.