Acts 28:27
For this people's heart has become calloused; they hardly hear with their ears, and they have closed their eyes. Otherwise they might see with their eyes, hear with their ears, understand with their hearts and turn, and I would heal them.'

Callus (definition) : a thickened and hardened part of the skin or soft tissue, especially in an area that has been subjected to friction.

A calloused heart means having calluses in the heart, emotionally hardened. This is the dangerous stage to be in. A calloused skin has no feeling. In the same way a calloused heart has no feeling.

How to get healed? The scriputre is calling us to make effort to see with our eyes, hear with our ears and understand with our hearts so that God can heal it.

Application

Is your heart calloused? If yes, it's time to treat it. Talk about your heart to someone who can guide you with God's word.