Call for Faithfulness
The writer pauses again in his exposition to deliver a second warning to his readers. This warning can thought of as in two segments. We will here consider the first of these segments which could be entitled: THE CALL FOR FAITHFULNESS. Knowing the immaturity of his readers the writer was anxious that his readers be aware of the incalculable loss they would face if they did NOT attend to his exhortation. His basic text for this exhortation was Psalm 95:7-11 – which he will expound on in the second segment [of this warning].
His readers were addressed as “holy brethren, partakers of the heavenly calling”. This was a brief reminder of what he had previously taught. They were indeed brethren - not only with one another but also with their Captain.  And they “shared [were partakers] in the heavenly calling” in that God was “bringing them to glory”. Thus the author was thinking especially of their high privilege of being invited to participate in the future dominion and joy of God’s King-Son. In light of this, they were to focus on the One who was both the Apostle and High Priest of their Christian profession - who is even now faithful to the God who appointed Him. They would find in Him a model for their own fidelity – as well as in Moses, His Old Testament prototype. Moses’ faithfulness - in erecting the Old Testament tabernacle [house] - provides a picture of Christ in His past and present ministry. Jesus, of course, is superior to Moses in honor but, in addition, the tabernacle Moses built was a miniature representation of “everything” - over which Jesus now presides in heaven.
Then, by a natural semantic shift, the writer moves from the thought of the house as the tabernacle [where priestly activities transpire] to the thought of the house as people who engage in these [priestly] activities. That is, his readers comprise the Son’s [priestly] house IF they [and we] hold fast their [our] confidence [courage] and the hope of which they boast to the end. This, of course, did NOT mean that his readers could forfeit their eternal salvation but rather THEIR ROLES IN THE SON’S PRIESTLY HOUSE. It was precisely this danger which concerned the writer in the present warning passage as well as in later ones.
 There are five warnings in this epistle. The first warning was found in Heb. 2:1-4. This second warning includes all of chapters 3 and 4.
 These segments are 3:1-6 and 3:7-4:11.
 See Heb. 5:12-14.
 Quoted in Hebrews 3:7-11.
 Heb. 3:1.
 Heb. 2:11-12.
 Heb. 2:10. The word share is the Greek word μέτοχοι metochoi = partakers, partners which is also used in Heb. 1:9, 3:14, 6:4, and 12:8. See also Luke 5:7.
 See Matt. 22:1-14. Also note Matt. 25:21, 23.
 Apostle probably points to the fact that Jesus was the One sent forth by God as the supreme revealer of the Father (Cf. 1:1-2).
 High Priest picks up the role mentioned in Heb. 2:17-18.
 Heb. 3:2s.
 Heb. 3:2b. Cf. Num. 12:7. This reference to Moses [“he was faithful in His house”] was in relation to the fact that Moses had constructed the tabernacle in strict obedience to divine direction (Cf. Ex. 39:32, 42, 43). The tabernacle was thus a prophetic testimony of things [like this writer is pointing out] that would be spoken in the future (Heb. 3:5).
 Because of the fact that the builder of the house has more honor than a servant [carrying out His directions] and because Jesus was involved in the “building” of everything [namely, creation (Heb. 1:2, 10)]. See Heb. 3:4.
 That is, the UNIVERSE (see verse 4). That is, Jesus now has a UNIVERSAL priesthood in heaven and is faithful over it (Cf. vs. 6a).
 See Heb. 1:3, 4:14. The Holy of holies was indeed God’s earthly house but it was a just a shadow of heaven itself where Christ has now gone to minister (Heb. 9:24). “Moses’ fidelity consisted in erecting that shadow house, the tabernacle, so that it could properly prefigure the future order of priestly activity which now has the universe itself as its proper sphere. This is the sphere where the exalted Christ sits faithful in all His current ministrations as well as past ones, functioning as a Son over God’s house”. [The Bible Knowledge Commentary]
 It is an error to identify “house” with the body of Christ [the true universal church]. As the context and Old Testament backgrounds shows, the author was thinking in priestly terms. He was also thinking functionally. The exalted Son presides over a priestly apparatus which they [his readers and ourselves] can presently be a part of. [The Bible Knowledge Commentary]
 Heb. 3:6b. Note that this is CONDITIONAL and the writer even includes himself (as he also did in his earlier warning – Heb. 2:1, 3) within the scope of his admonition.
 Which Jesus clearly taught they could NOT [Cf. John 6:35-40 and many, many other passages].
 Which is only maintained by holding firmly to their Christian profession [Cf. Heb. 3:14, 10:23-25, 35-36]. “As long as the readership held firmly to their Christian commitment, they also functioned within this priestly arrangement [over which Jesus was presently presiding]. But just as one who was a true Levite by birth could withdraw from participation in the tabernacle of Moses’ day, so too one who is truly a Christian by new birth may withdraw from his priestly role within the functioning household.” [The Bible Knowledge Commentary]