Hebrews contains a number of warning passages and this is one of the sternest. It is not a passage that is meant to make us comfortable, but nor does the writer simply want to unsettle our faith. Rather he wants to drive us to the place where real confidence is to be found and enjoyed.
Chapters 3 and 4 had spoken of the generation in the wilderness, which had experienced God’s deliverance and many signs of His grace, and yet missed out on the Promised Land because of their unbelief. They were a warning, an example to avoid (4:11), and not an idle warning: could it happen to me? YES, which is why I must give careful attention to these words.
The writer chides them for being “slow to learn” – literally sluggish or lazy in their hearing. It is not an intellectual problem but a spiritual one: instead of being hungry for God’s Word, they have lost their appetite and seem reluctant to listen and pay attention to God’s Word (cf. 2:1). They are acting like babies, wanting only milk, when they should have progressed beyond that. A milk only diet is right and proper for newborns, but not as we get older. What they should be feeding on is “the teaching about righteousness”, a phrase commentators take in different ways, but seems at the very least to imply a fuller, deeper understanding of the Gospel that impacts how we live (v.14).
The “elementary teaching” they are wanting to go back to is unpacked a little in 6:1,2 and doesn’t bear much resemblance to a typical Christianity Explored syllabus! Strikingly there is no mention of Jesus (it is teaching about Him in chs7-10 that the writer thinks of as “solid food”), and perhaps refers to the foundational framework of understanding which the OT Scriptures give, on which an understanding of the Gospel can be built. The original readers of this book were Jewish Christians, tempted to drift back towards Judaism, which the writer is saying is like going back to a milk-only diet, or demolishing the house and just having the foundation (which is not good on its own, it offers no shelter).
There is a point of no return, these verses warn. Those described in vv.4,5 certainly seemed like Christians, they had been exposed to the Gospel, understood it, experienced something of its power, second-hand at least. They looked like Christians and no doubt had thought they were; but we have already been reminded that “we have come to share in Christ [only] if we hold firmly till the end the confidence we had at first” (3:14), and that need to persevere will be something the writer returns to (eg. 10:36-39). To “fall away” means much more than simply to backslide, it is “crucifying the Son of God all over again”, a deliberate rejection of Christ by someone who knows what they are doing. The writer fears some of his readers are heading down that road, not that they are there yet (v.9), and is warning them where that road heads and the need to turn around quick, while they can. He has seen enough evidence in the past that their faith is genuine (v.10), signs of a good crop and not merely “thorns and thistles”, but they mustn’t become “lazy” (the same word used back in 5:11 of that spiritual laziness that pays little heed to God’s word).
Although the proofs of their faith are cause for encouragement, the proper grounds for confidence lie not in ourselves but in God – in His Word. The writer refers back to God’s promise to Abraham, which undergirds all the Gospel promises that follow. Indeed what was promised to Abraham was ultimately realised through Christ, so when he speaks in v.17 of “the heirs of what was promised” he is speaking of us. God has both promised, and confirmed the promise with an oath, and because we know “it is impossible for God to lie” (v.18) we have doubly-sure grounds to be absolutely confident.
Our hope is like an anchor, secure in heaven, because that is where Christ is. His presence in Heaven now guarantees our hope. He, we might say, is the anchor, and we must hold fast to Him (for He is God’s word to us (1:2). All of us could have “a sinful unbelieving heart that turns away from the living God” (3:12), our tendency is to become lazy in listening to God’s Word. The warnings in this passage are intended to drive us back to Christ, so that we cling to Him in whom alone security and hope are to be found.