The context of the notoriously difficult “falling away” passing in Hebrews 6:4 is critically important. In Hebrews 6:1-3 the author of Hebrews implies his readers are immature and have failed to grow at an expected pace. They need to “build again” on the foundation and re-learn the basics of the faith. In all of the Jewish Christian literature, there is a struggle to integration Judaism and Christianity. How much of the “old covenant” ought to be brought over to the new faith? Hebrews 6:1-3 lists six foundational items (three pairs), all of which fit into the Jewish Christian world of the original authors, but need to be considered in the light of the New Covenant.
Repentance from Sin. Both Peter (Acts 2:38) and Paul (Acts 17:30-31, 26:20) preach repentance from sin in the book of Acts. Although turning to God is turning away from sin, the phrase “acts which lead to death” is unique to Hebrews 6:1. It is similar to James 2:17, “dead faith.” The original readers of Hebrews were not pagans converted from a sinful life, but faithful Jews who may have been (from an Old Covenant perspective), not all that sinful. The emphasis is on unproductive works vs. faith. So what exactly needs to be confessed and repented of when one comes to Christ? Perhaps the readers are overly concerned with outlining the exact nature of that repentance rather than repenting and then maturing!
Faith in God. Perhaps this is simply the natural partner of “works which lead to death,” the active sense of repentance. Since the audience is Jewish, it is unlikely that they worshiped idols. The acts that lead to death and faith in God have to do with their participation in salvation, two sides of the same coin.
Instruction on Baptisms. The word “teaching” here may be an introduction to the final four items since they are all under the heading of “teaching.” This is a fairly difficult exegetical problem; the noun didach'” was used at the end of the first century of a body of instruction on these sorts of things (Didache, for example). That the noun for baptism is plural is a strong indication the readers were still practicing Jewish ceremonial washings in mikvoth. If this is so, then either this is evidence Jews in Rome practiced ritual purity at a much higher level than we might have thought, or that the book of Hebrews was sent to Jerusalem, where there is clear evidence of mikvoth and ritual washing. In either event, plural “baptisms” likely does not refer to Christian baptism as we understand it, an “initiation ritual.”
Laying on of Hands. Like baptisms, it is tempting to read this in terms of later Christian practice, but “laying on of hands” was practiced in Judaism before it was taken over by Christians (Gen 48:14, Num 27:15-23, Deut 34:9). Since this is paired with baptisms, it is possible that laying on of hands was associated with the beginning of Christian life in the Jewish churches (Cf. Acts 8:16-17, 19:5-7).
Resurrection of the Dead. The final pair in this list are not practices but doctrines which were subject to strong (and perhaps emotional) debates among first century Jews. One only needs to recall the division between Sadducees and Pharisees to know that the resurrection was a controversial issue (both for Jesus, Mt 22:23-33) and Paul, Acts 23:6).
Eternal Judgment. A related theological problem in first century Judaism was the final judgment. If there is a resurrection in the future, what will happen to those who are raised from the dead and condemned? Is there “eternal torment”? There are a number of texts from the Second Temple period which describe eternal torment of the unrighteous dead. 2 Enoch and 3 Enoch, for example, seem to indicate that at least some Jews of the first century did think that the dead would face eternal (and sometimes ironic) punishment.
The author does not say these “foundational items” are unimportant, but that these ought to be settled by now to that the readers are ready to move on to more mature doctrines. The “deeper” things in this case is next section of Hebrews, the teaching on Melchizedek and the Tabernacle. The readers are fretting over foundational issues (who is in/out, details of theology which are not critical), and they are therefore unprepared for the difficulty of the argument which he is about to make.
But more important for the writer of Hebrews, the readers are unprepared for the possibility of persecution. If they have not progressed beyond the first things of the faith, will they be willing and able to endure physical persecution in the near future? Are the mature enough to continue in their faith in Jesus?
It is fairly easy to draw some analogies to Christian maturity in the western church. Although there are some large and wealthy churches, it is possible most members of those congregations have not moved much beyond the basics (an initiation ritual and when to stand for worship, basic teachings or what political party to support). Just as for the audience of Hebrews, when persecution comes, these will not be enough to ensure loyalty to Jesus Christ.