The Heinous Sin of Unbelief

October 24th, 2025
by Lance Waldie

Hebrews 3:15-19 While it is said, “Today if you hear His voice, Do not harden your hearts, as when they provoked Me.” 16 For who provoked Him when they had heard? Indeed, did not all those who came out of Egypt led by Moses? 17 And with whom was He angry for forty years? Was it not with those who sinned, whose bodies fell in the wilderness? 18 And to whom did He swear that they would not enter His rest, but to those who were disobedient? 19 So we see that they were not able to enter because of unbelief.

The Israelites had lived in Egypt circa 1850-1450 BC, being subjected to slavery for at least half of that time. After having witnessed God’s mighty power in the ten plagues God inflicted on Egypt through Moses, the final plague being the death of the firstborn during the Passover, by 1446 BC God brought Israel out of Egypt. On the way out, Israel watched God part the waters of the Red Sea and wash their Egyptian pursuers away in the waters. As they traveled through the wilderness, they observed God directing them with a cloud by day and a pillar of fire by night, enjoying daily bread (called manna) that God miraculously provided for their sustenance. Likewise, they enjoyed the water God provided for them from a rock to quench their panging thirsts. So, Israel saw God firsthand with proof after proof of His love and provision for them. Astoundingly, they failed trust God and were satisfied only temporarily after seeing Him mighty works. The Israelites of that generation illustrate the hard and unbelieving heart. In the face of overwhelming evidence of God’s love, they later rejected and spurned Him.

Now for the third time, the author of Hebrews quotes from Psalm 95:7-11 in order to make his point. The first time he quoted it in 3:7, it was an illustration of Israel’s disobedience in the wilderness. The second time was a simple reference to “today” in 3:13 to show the urgency needed to return to their former commitment to Christ. Now when the author quotes it again in v. 15, his exposition focuses on rebellion. His point is to encourage the audience to heed the calling of Jesus by emphasizing the dire consequences of disobedience stemming from hardened hearts.

The author emphasized his argument with three rhetorical questions and a conclusion in vv. 16-19. His point is that those who failed to enter God’s Promised Land, Canaan, were the same ones who had heard God’s promise about Canaan yet refused to trust Him (v. 19). So, in His fury God closed the doors of Canaan for that generation (Num. 14:21-35). The audience was given this illustration because they were in danger of the same rebellion their forefathers committed 1500 years prior. The author concludes in v. 19 that an unbelieving heart will most certainly forfeit God’s blessings. And those who refuse to believe have only themselves to blame.

The rebellion of Israel is described by the author with four different terms. First, v. 16 says that Israel “provoked” God (“to make angry”). Second, v. 17 says that Israel “sinned” (“to miss the mark”). Third, v. 18 says that Israel was “disobedient”(“to refuse to believe”). Fourth, v. 19 says that Israel was characterized by “unbelief” (“refusal to trust”). Truly, Israel was like wax which is naturally hard but melts when put under heat. But once the heat is removed the hardness returns. Their flesh was weak from the deceitfulness of sin. They needed continued faith to remain soft and the encouragement of other believers, just like all Christians today!

Food For Thought
True faith (salvation) cannot be lost. It is given by God as a gift, and it comes by His grace through our faith in Christ. But we must continue in our faith and endure to the end (Matt. 13:20-21; Acts 11:22-23; 13:43; 14:21-22) in order to prove ourselves God’s true children. Salvation is to be “worked out with fear and trembling” (Phil. 2:12). Yes, we are “kept by the power of God,” but how God keeps us is “through faith” (1 Peter 1:5). Our abiding faith must endure.