The Bible is full of examples, both good and bad. The New Testament writers were inspired to use those examples for our learning (Rom. 15:4). There is a section of Scripture in Hebrews chapter three that highlights an attitude that would keep us out of heaven.
“Take care, brethren, that there not be in any one of you an evil, unbelieving heart that falls away from the living God” (Heb. 3:12). The writer of Hebrews uses the examples of the children of Israel wondering in the desert as an example of what it means to fall away from God. There were three things mentioned that they did. They hardened their hearts, they went astray in their hearts, and they didn’t know God’s ways (3:8, 10). These are not hard to find in the people of today. Even in Jesus’ day people had the same problem. Quoting from Isaiah He said, “For the heart of this people has become dull, with their ears they scarcely hear, and they have closed their eyes, otherwise they would see with their eyes and hear with their ears, and understand with their heart and return, and I would heal them” (Matt. 13:15). It is clear that this is a human problem. From the beginning, people have struggled with this. The writer of Hebrews shares with us how this hardening happens—“you will be hardened by the deceitfulness of sin” (3:13b).
The reason why this is a human condition is because sin is a problem we all have to face. Choosing to follow and believe in God is not because there is a lack of evidence. Those that spoke directly with God and saw His wonderous works didn’t always obey. Those in the wilderness believed that God existed, that He was a real entity. However, they did not obey. Belief alone is not enough to get us into heaven. Every time we choose sin over obedience, we have hardened our hearts a little more toward God. “For if we go on sinning willfully after receiving the knowledge of the truth, there no longer remains a sacrifice for sins” (Heb. 10:26). You can harden your heart to the point that you would never return to the sacrifice for you sins.
What can we do to keep our hearts from hardening? Stay away from sin as much as possible. “Work out your salvation with fear and trembling” (Phil. 2:12b). We also have this encouragement, “But encourage one another day after day, as long as it is still called ‘Today,’ so that none of you will be hardened by the deceitfulness of sin. For we have become partakers of Christ, if we hold fast the beginning of our assurance firm until the end” (Heb. 3:13-14). There is a sense in that we need to help one another not get to the point of having a hardened heart toward God. In doing so we “hold down” or “seize onto,” as this word suggests, the assurance we had at the beginning of our faith in God.