“Take care, brothers, lest there be in any of you an evil, unbelieving heart, leading you to fall away from the living God.” Hebrews 3:12 (ESV)
The context of this passage from the book of Hebrews is that the author has been challenging the readers not to rebel as the Israelites did in the wilderness in the days of Moses. But what did the Israelites actually do? Reading through Deuteronomy 1 you can see Moses laying out the case. We see that the last straw was when the Israelites believed the report of the ten spies rather than the report of Caleb and Joshua. The people believed they would be killed by the giants of the land — the land that God promised to them. In verse 27 we see that the Israelites actually believed God hated them. By the end of chapter 1, we see that the people never really trusted God.
We must take care to heed this warning ourselves. Many people in churches today believe more in the punishment of God than they do in the favor and blessing of God — that God is as likely to be against them as for them. Yet here in Hebrews we are warned that when we don’t believe in God’s favor and blessing toward us, our hearts are actually evil and unbelieving. That implies that our belief needs to be more than just that Jesus saved us, but that he saved us so that we might have life, and have it abundantly (John 10:10)!
This is a very serious warning in Hebrews, and follows and intertwines with a phrase the author uses repeatedly, talking about entering God’s rest. We enter into God’s rest by trusting in His work on the cross, and not in our own work after we have put our faith in Him. This warning tells us that we are in danger of falling away from true faith if we fail to trust in Jesus’ work being sufficient for all we need. If we trust in that, we can rest from our work and our striving, and look to see the blessings that God continually pours out on us.