A callus is a toughened area of skin which has become relatively thick and hard in response to repeated friction, pressure, or other irritation. Since repeated contact is required to form a callus. Normally, a callus will form on any part of the skin exposed to friction over a long period of time. (Examples: the middle finger due to writing, fingers used to play a stringed instrument…)
A heart can become callused (hardened) by repeatedly resisting the Holy Spirit. It can also be caused by repeatedly failing to act upon what you have heard God speak to you through His Word, sermons/messages, or the Holy Spirit. Basically a callused heart is caused by ignoring the Holy Spirit.
After a heart becomes callused the person will feel less and less of the Holy Spirit’s convicting power and His warnings.
Proverbs 29:1 NKJV
“ He who is often rebuked, and hardens his neck, Will suddenly be destroyed, and that without remedy.”
God will judge those who stubbornly reject His correction.
Hebrews 3:7-9 NKJV
“Therefore, as the Holy Spirit says: “Today, if you will hear His voice,
Do not harden your hearts as in the rebellion, In the day of trial in the wilderness,
Where your fathers tested Me, tried Me, And saw My works forty years.”
Your heart can become callused even while sitting in the church or doing ministry work. When we hear the Word of God we must apply it to our daily lives.
James 1:22-25 NKJV
“But be doers of the word, and not hearers only, deceiving yourselves. For if anyone is a hearer of the word and not a doer, he is like a man observing his natural face in a mirror; for he observes himself, goes away, and immediately forgets what kind of man he was. But he who looks into the perfect law of liberty and continues in it, and is not a forgetful hearer but a doer of the work, this one will be blessed in what he does.”
The Bible sin as to know to do right and not do it.
James 4:17 NKJV
“Therefore, to him who knows to do good and does not do it, to him it is sin.”
During Bible days, much like today, people love to hear powerful teachings but they fail to act upon or obey what they hear.
Ezekiel 33:30-32 NKJV
“As for you, son of man, the children of your people are talking about you beside the walls and in the doors of the houses; and they speak to one another, everyone saying to his brother, ‘Please come and hear what the word is that comes from the Lord.’ So they come to you as people do, they sit before you as My people, and they hear your words, but they do not do them; for with their mouth they show much love, but their hearts pursue their own gain. Indeed you are to them as a very lovely song of one who has a pleasant voice and can play well on an instrument; for they hear your words, but they do not do them.”
The people were eager to go to hear Ezekiel, and they would invite others to do so also, however they never applied it to their lives. They did not obey the Word that they heard. Their behavior did not match up to what they confessed as their beliefs.
Like many that were eager to hear Ezekiel, many attend church today as a form of entertainment or social gathering. Today many hear God’s Word but they do not put into practice what they hear.