3:1 Therefore, holy brothers [and sisters], partakers of a heavenly calling, consider the apostle and high priest of our confession, Jesus,
With this "therefore," the author continues to show the superiority of Christ to the old covenant and to urge the audience to continue in faith. In 2:17-18 he has introduced the idea of Christ as high priest. In 3:1 the author begins to "consider" him. The sense of him as an apostle to us echoes comments in chapter 2 that relate to Christ partaking of flesh and blood in order to lead us to glory.
The heavenly calling either refers to the place from which God calls us or the place to which we are called. Hebrews, in my opinion, fits more with the popular Christian sense of dying and then going immediately to heaven than some of Paul's writings do (although 2 Corinthians 5 may indicate that Paul himself came to this view). Resurrection is certainly present in Hebrews (6:2; 13:20). The question is what the author understands it to be.
Some debate has taken place over the years over what exactly the "confession" might be. Predictably, those from higher church contexts tend to see it as a specific confession of faith of some sort, such as "Jesus is the Son of God." Those from lower church contexts tend to see it somewhat metaphorical as having faith.
Given that the early church apparently used confessions, perhaps in association with baptism, it seems not unlikely that the author did have a specific confession in view. The confession "Jesus is Lord" is well attested in Paul (e.g., Rom. 10:9), but we have no good evidence to see it in Hebrews. Some have suggested "Jesus is the Son of God," since Christ's Sonship is a major part of Hebrews Christology (cf. Acts 8:37 in late manuscripts).
Another intriguing possibility is the early Aramaic affirmation "Our Lord, come," "marana tha" (e.g., 1 Cor. 16:22). It would fit the particular issues of Hebrews well. We simply do not have enough information to know exactly what confession the author specifically has in mind.
3:2 ... who was faithful to the One who made him as also Moses [was] in his house.
In chapter 1 the author poetically proclaimed that Christ was greater than the angels. In these six verses the author will show that Christ is greater than Moses. Within Judaism, this would have been an astounding claim. For so many Jews, Moses took precedence over any other figure in all of history, including Abraham.
The subtext of the contrasts between Christ and angels/Moses is that of the law. In 2:2 the author reminded us that Jewish thought at this time saw the law coming to Moses at the hands of angels. To say that Christ is greater than angels or Moses is thus to say that he is a more significant mediator between God and humanity than any other.
House here means household. We have to adjust our thinking to remember that the household at this time is not merely two parents and two and a half children but the extended family as well including servants. Caesar's household, for example, presumably included the whole Roman administrative system.
The question of "making" Christ was of course part of the Trinitarian debates of the 300's. The word can also mean "appoint." Mark uses it of when Jesus "makes" or "appoints" his disciples.
3:3 For this [Jesus] has been deemed worthy of greater glory than Moses in as much as the person who builds the house has greater honor than the house.
Paul had also contrasted the glory of Moses with the glory of the new covenant in 2 Corinthians. Here the author shifts from house=household to house=building. Jesus builds the house, makes it happen. Moses is a part of the house--a servant as we will see.
3:4 For every house is built by someone, and the one who built all things is God.
Once again we see that it is only in the poetic context of Hebrews 1 that Christ is declared to be the agent of creation. Here God is the ultimate builder.
3:5 And Moses, on the one hand, was faithful in all his house as a servant to witness to the things going to be spoken,
This verse is an allusion to Numbers 12:6-8: "If a prophet of the Lord should arise among you, I will be known to him in a vision and I will speak to him in a dream. It is not this way with My servant Moses. He is faithful in all My house. I will speak mouth to mouth to him..." (LXX). The author seizes on the mention of Moses as a servant to show in the next verse that Jesus is the Son.
The "things going to be spoken" are surely the "word of salvation" that was first spoken by the Lord (2:3). When we get to chapters 7-10, we will see that the author of Hebrews saw the literal practices of the Pentateuch, the book of Moses, as filled with shadowy illustrations of the reality in Christ. The Law is thus a witness to the things going to be spoken through the Lord.
3:6 ... but Christ [was faithful] as a Son in his house, whose house we are, if indeed we hold fast to confidence and the boasting of hope.
With this comment the author makes the contrast between Christ and Moses clear. Moses was only a servant in God's house. Jesus was a Son.
We notice that membership in the household of Christ is conditional. The author uses an intensified form of condition, "if indeed." The whole sermon of Hebrews is in fact about the need to hold fast in confidence, not to give up faith. To keep believing in that for which we hope. Faith is the substance of things hoped for, the evidence of things not seen. Only if we hold fast to this confidence and this hope can we remain in the household of God.
3:7-19 make it overwhelmingly clear that this is what the author has in mind.