Hebrews 5:11-14: The Diagnosis
At this point in the epistle, the author of Hebrews must take a detour. His intent was to continue speaking about the connection between Jesus and Melchizedek, but he has run into a problem: the audience is suffering from a “dull” faith (5:11), and they cannot understand what comes next. Thus, an excursus is in order.

Important to note, this dull faith is an acquired situation because the Christians had become lazy, or sluggish, in their faith. While they should not only be able to comprehend where the author desires to go, by now they should also be mature enough to teach others. Instead, they require the elementary things of Christ to be taught to them again and again (5:12). They are living on spiritual milk, and do not have a diet of the Word and practice of faith that will allow them to mature properly. Their condition is most evident in their inability to “discern good from evil” (5:14). They have two responses: remain on milk or make a diet change.

Hebrews 6:4-8: The Wrong Response—Continue to Drift
First, despite what John Wesley believed, this is not a passage that debunks the doctrine of the “Perseverance of the Saints.” There are too many other verses that affirm this doctrine (John 10:28-30, 6:37-38; Romans 8:38-39, etc).

Second, context is king. The author has built his entire case thus far from the Old Testament, so we should look to the Old Testament to explain this confusing text. This can be accomplished by reading Numbers 14:2-4, in which the Israelites request someone to “lead them back to Egypt” (Num. 14:4). Despite all that they had seen God do, they did not trust him because their faith was intellectual and not internalized. Thus, all Israel is not true Israel. The visible church is not necessarily the invisible church. Just as not every Israelite was saved, even though they experienced the blessings of Yahweh as a nation, everyone who claims Christ is not either. The logical end of someone who chooses to remain on milk is apostasy, whether that be returning to Egypt, Babylon, or Judaism.

“They went out from us, but they were not of us; for if they had been of us, they would have continued with us. But they went out, that it might become plain that they all are not of us.” -1 John 2:19

Bringing this all back to the diagnosis of weak faith in 5:11-14: the wrong response is to remain on milk, to refuse to internalize the Gospel, and be sluggish in our faith.

Hebrews 6:9-12: The Right Response—Practice.
If the wrong response is the remain complacent and drift away from holiness, then the right answer is to practice your faith. This is done by loving others and serving the saints (6:10). The result of this practiced faith is fruit. And this fruit brings assurance.

You will be known by your fruit (Matt. 7:16).