Converted to what?

"13 Therefore speak I to them in parables: because they seeing see not; and hearing they hear not, neither do they understand.

14 And in them is fulfilled the prophecy of Esaias, which saith, By hearing ye shall hear, and shall not understand; and seeing ye shall see, and shall not perceive:

15 For this people's heart is waxed gross, and their ears are dull of hearing, and their eyes they have closed; lest at any time they should see with their eyes and hear with their ears, and should understand with their heart, and should be converted, and I should heal them."
https://www.biblegateway.com/passage/?search=Matthew+13&version=KJV