"Today if you will hear His voice, do not harden your hearts..." (Heb. 3:7) The great danger that is always present is that we will harden our hearts to a point where we cannot hear God. How is this possible? There are perhaps three areas that stand out, among all others. They are unbelief, disobedience, and neglect.
The first thing that we are called to do is to believe the word that God speaks to us. When He communicates Himself to us, our work is to believe (Heb. 11:6, 4:2). Doubting breaks our relationship with God. He cannot direct us, because we have questioned His character. We cannot receive, because we have shut off the source. On the other hand, when we believe God, it opens up the channel of grace to our hearts and lives. His word is supreme, and God is behind His word to fulfill it in our lives.
He does not consider our ability or natural reasoning. He knows what He is doing, and all He asks is that when He speaks, we believe His word. Scripture is full of examples of those who believed and those who did not believe. It is the same for us--let us believe the word that comes to us, and it will form the basis for obedience.
The second way we can harden our hearts is through disobedience. We believe the word of the Lord at first, but then we do not act upon it. It was good when it came to us, and we said, "Yes, Lord," but then we did nothing. If we do not go on to obey, the word does not feed us. It is the "engrafted word" which is able to save our souls, and the word becomes engrafted only when we obey. This is where we experience God, and know His grace.
If we do not obey, our spiritual senses start to become dull. It happens slowly, and we do not realize what is happening. We no longer have an ear for God. His word seems heavy to us, no longer a delight. Our first love begins to wane. Why? Because we have not acted on His word. God speaks for us to obey. Our love is proven by our obedience (John 14:21).
The third way we can harden our hearts is through neglect. This is actually a form of disobedience, but it is more subtle. We don't directly disobey a known command. We just don't give attention to our relationship with God. We do not set aside time for God to speak to us and commune with us. The days pass into weeks and years, and our hearts become hard and indifferent. We no longer care whether we hear God or not. We are led by our own minds, our own wisdom, and what we want to do. We still acknowledge God in our minds, but our hearts are far from Him. We have left the abiding place, and leave no place for God to speak to us. The opposite of this is attentiveness and alertness in our relationship. Our ear is keen, and every aspect of our relationship with God is given the utmost importance. As our spiritual senses are exercised, we become more alert to His presence and His communication to us. We learn to know His voice. How wonderful that place is, and how the riches of His love are opened to us!