12 Beware, brethren, lest there be in any of you an evil heart of unbelief in departing from the living God;
Now in verses 12-19 the Holy Spirit applies the lesson of verses 7-11 to Christians. He warns the readers of Hebrews not to commit the same kind of negative volition that the original Israelites committed.
The word “beware” is a word of urgent warning. It is amazing that the Israelites could observe the 10 plagues in Egypt, the deliverance at the Red Sea, and the events at Sinai and yet persist in their unbelief.
Note that it is “brethren” in question, not non-Christians. Nowhere does Hebrews indicate that the audience was unbelievers. Neither is there any indication here that these people were mere professors but not real believers. Note the phrase “holy brothers” in verse 1.
lest there be in any of you an evil heart of unbelief
The issue of an “evil heart of unbelief” has to do with Hebrew Christians of the first century who were about revert into Judaist practices (He 3:10). They were not to do what God’s people did in the wilderness. “Unbelief” is the kind of sin that the original Israelites committed.
They committed unbelief with an “evil heart.” “Evil” is active opposition to God. This sin corrupts both self and others by pernicious actions. This evil is not passive or latent but active in the soul. These people have reached a place of active opposition to God. This action is entirely controlled by unbelief where no faith can be found whatsoever. The Lord questioned Moses at Kadesh, “How long will they not believe in Me?” (Nu 14:11). The Lord described this unbelieving heart as “evil” twice (Nu 14:27, 35).
“Unbelief” has nothing to do with personal salvation but of failure to claim the promises of God for our daily lives. Israel failed to believe what God promised.
in departing [turn away]
The word “departing” is the Greek word to apostatize. It comes from two Greek words: off and to stand. Thus, the idea is to stand off from, giving the idea of withdraw. This word is not a technical term for absolute apostasy (ἀποστῆναι). The idea is simply to move away from a point of reference (Lu 2:37; Acts 12:10; 15:38). Israel withdrew from God’s Word and promises. They would not listen to His voice. Here “depart” does not mean to leave Christianity; it has the lesser meaning of departing from what God promises. This is the thought presented in the historical section as well (Numbers 14:9 LXX).
These words explain the previous phrase “an evil heart of unbelief” (ἐν τῷ with the infinitive ἀποστῆναι is used epexegetically). The Hebrew readers did not see the claims of Christ clearly. The word “departing” thus means to turn away. The idea is to rebel against God’s promises (Nu 14:4, 9; Dt 1:26).
It is dangerous to interpret New Testament Greek words with theological baggage. The argument is not theological apostasy here. The term here describes disobedience that brings divine discipline, illustrated in Moses’ day. Numbers 14:20 says that God forgave Israel in response to Moses’ prayer. God protected Israel for the next 38 years in the desert. They did not lose their salvation but the opportunity to enter the Promised Land. They did not lose their covenant privileges with God.
The readers of Hebrews had previously believed in Christ as the Messiah exclusively but now were in the process of leaving exclusive trust in Him for Old Testament convictions. They wanted to go back to the Old Testament priesthood and sacrifices.
Christians need to trust God to meet them in their time of need.
The sin of Israel was grievous, but it was not a complete rejection of faith in God. God “pardoned them” by His lovingkindness (Nu 14:19-20). The people mourned greatly over God’s judgment on them and confessed their sin (Nu 14:39-45). Both their forgiveness and the failure were part of the same oath.
The caution in this verse is not against a complete departure of faith in God. The problem with the readers of Hebrews was a lack of faith that He would meet them in a time of need (He 2:18; 4:16). Both Moses and Aaron were punished at the same time and with the same discipline received by the generation that came out of Egypt. They also received the same punishment at the same time. The identical Hebrew words are used of them as the sin of the people, “rebellion” (מָרָה) and “unbelief” (לֹא אָמֵן). Note these verses: Num. 14:9, 11; 20:12, 24; Deut. 9:23–24.