Today, if you hear his voice, do not harden your hearts. Hebrews: 3:7-8

What is meant by hardening of our heart?

Gill's exposition of the entire Bible has a beautiful explanation for it, which I wish to share: (sorry it is one very long sentence, but if you pause and read it you will get it.)

There is a natural hardness of the heart; the heart of man is like a stone, destitute of spiritual life, motion, and activity; it is senseless, stupid, impenitent, stubborn, and inflexible, on which no impressions can be made, but by powerful grace: and there is an acquired, habitual, and voluntary hardness of heart, to which men arrive by various steps; as entertaining pleasing thoughts of sin; an actual commission of it, with frequency, till it becomes customary, and so habitual; an extenuation or justification of it, and so they become hardened against all reproofs and sermons, and to all afflictions and judgments; are insensible and past feeling, and openly declare for sin, and glory in it: and there is a hardness which God's people are liable to, and should guard against; and which is brought on by a neglect of private and public worship, and by keeping bad company, and through the ill examples of others, and by giving way to lesser sins; for all sin is of an hardening nature...

 Is our heart harden today? Have we become insensitive to the Holy Spirit? If we have the slightest doubt we need to work on it.

 I will give you a new heart and put a new spirit in you; I will remove from you your heart of stone and give you a heart of flesh. Ezekiel 36:26