I have noticed that, among the (small subset of) Christians that I have either talked with or read their works or listened to their letures or sermons, discussion about the place of obedience and steadfastness in relation to the Christian life is often reduced to and exclusively treated in regards the relationship between obedience and (initial) salvation. Put another way, when we hear terms such as 'obedience' and 'faithfulness' it is all too easy to synonymize this with "works" and, thus, especially in Protestant discourses, focus exclusively on the role or non-role of works in (initial) salvation. This is, indeed, quite warranted, given the various extremes that have been expressed and held in the history of the Church. Yet, if we (purposefully or otherwise) hold to such an exclusive treatment of this element in relation to Christian life as only pertinent to entry into life in Christ (even in light of the importance of such discussions), we potentially lose sight of its continual significance after the event we (that is, some of us) refer to as "salvation." This often creates a bit of a confusion among many (at times, myself included) Christians when we encounter exhortations towards obedience, faithfulness, steadfastness, perseverance, and the like, which abound in the New Testament. To give a concrete example, Jesus tells His disciples during the "upper room discourse," "If you love Me, you will keep my commandments" (John 14:15, emphasis added). Soon after, He reiterates this principle by emphasizes not only "having" His commandments, but "keeping" them, and this is evidence of our love towards Him (see 14:21, 23-24; 15:10). But, so many times we are at a loss with regards to how these apply for the Christian who believes in Christ, since we relegate things like "obedience" and "steadfastness" and "faithfulness" to the category of "works" that is not necessary for "salvation." This can result in an extreme position of rejecting these mindsets in our lives, since we fear that we might espouse a "works-based salvation" (again, referring mainly to initial salvation with disregard to its processual characteristics [see, for example, Philippians 2:12; 1 Timothy 4:16; Hebrews 9:28; 1 Peter 1:5, 9; 2:22]). Thus, without an understanding of obedience in love (see John 14:15), many of us are or have been in the position of those in the 1st century church in Rome, to whom Paul was obliged to pen the now infamous rhetorical question, "Are we to continue in sin so that grace may increase?" (Romans 6:1). We are (often), therefore, utterly ignorant of how to apply the biblical concept of obedience in the Christian life, which, by God's grace, we enter in through Christ ("by grace through faith," see Ephesians 2:8).
With this in mind, I would like to pause briefly on the conditional clause "if we hold fast" in Hebrews 3:6. For, similar to prior exhortations aimed at encouraging obedience and perserverance (see 2:1; 3:1), it sets a trend for a series of content similar exhortations to "believe" and "obey" (or "not disbelieve/not disobey") in the third chapter and beyond. Hebrews specifically, and the New Testament generally, are rife with such exhortations, which out to impel us to seek God for an understanding of how this ought to operate in regards to the life He has given us in Christ, which we now presently experience. The conditional element "if we hold fast" relates back to the expression that we who believe in Jesus are part of His/God's "house." Therefore, we can perhaps maintain that this type of steadfastness and, in a sense obedience by faith (which becomes clear as we read on in Hebrews), is extremely important if not to some degree necessary for being counted among those who comprise Christ's house. This imagery is explained in greater detail by Peter in his first epistle:
And coming to Him as a living stone which has been rejected by men, but is choice and precious in the sight of God, you also, as living stones, are being built up as a spiritual house for a holy priesthood, to offer up spiritual sacrifices acceptable to God through Jesus Christ. For this is contained in Scripture: 'Behold, I lay in Zion a choice stone, a precious corner stone, and he who believes in Him will not be disappointed.' This precious value, then, is for you who believe; but for those who disbelieve, 'The stone which the builders rejected, this became the very corner stone,' and, 'a stone of stumbling and a rock of offense;' for they stumble because they are disobedient to the word, and to this doom they were also appointed. But you are a chosen race, a royal priesthood, a holy nation, a people for God's own possession, so that you may proclaim the excellencies of Him who has called you out of darkness into His marvelous light. (1 Peter 2:4-9, emphasis added)
This passage serves as the substance by which Peter urges his readership towards faithfulness and obedience (see, for example, the rest of chapter 2), although their relationship with Christ (being in Him) is not predicated on such. Note the similarity in language between Peter's epistle and the epistle to the Hebrews: just as we are the "house" of Christ "if we hold fast the confidence and the rejoicing of the hope firm unto the end," as in Hebrews, so we are "built up as a spiritual house" with Christ as the chief cornerstone so that we might "offer up spiritual sacrifices" and "proclaim the excellencies" of God. In short, both of these passages resonate with the importance of, to use Jesus' language in the book of John, "keeping" His "words" and "commands" if indeed we love Him. Does this in any way mean that our initial salvation, our entrance into Christ and His body, depends upon obedience and faithfulness, which is perhaps to say, "works"? I maintain that biblical Christianity will clearly and definitively dictate that the answer to this is "no." For, as Paul writes, we are not justified by works of the Law (Romans 3:20, 28; Galatians 2:16). Or, to use the quintessential Pauline example, we agree that Abraham was justified by faith since he believed God (see Romans 4).
But this begrudgingly brings us back to our original predicament: What is the role of obedience in the life of a Christian if it is not necessary for (initial) salvation? If we do not understand the answer to this question as properly as is possible for us, we will not understand the exhortations in Hebrews (and elsewhere in the NT) which are directed toward believers in Christ to persevere and obey. Not without irony, I believe the resolution to our conflict is found in a somewhat paradoxical passage in James that appears to be in direct opposition to Pauline soteriology. Speaking of the relationship between faith and works, James writes that "faith, if it has no works, is dead, being by itself" (James 2:17). And he pushes the relationship further still, declaring that "a man is justified by works and not by faith alone" (2:24). If you didn't catch the supposed contradiction, reread that verse along with Romans 4, and then return to James' discussion of Abraham, of whom it is said that "as a result of [his] works, [his] faith was perfected" (2:22).
This last verse gives us a glimpse of hope in understanding this issue (to the degree that we can), maybe not by "resolving" it per se, but allowing for the mystery and admitting the mutual compatibility of these passages in a biblical framework. Justification is truly grounded in faith (and that in Christ), but the genuineness of our faith is manifest and, in some way as James indicates, "perfected" by works and obedience. Therefore, it is not surprising that, as we read Hebrews and consider its original audience who appear to be believers in need of encouragement and perseverance, we find multiple exhortations aimed at producing steadfastness and obedience that relates to our being part of Christ's "house." We, just as they, who are believers in Christ who are saved "by grace through faith," have continual need to press on "firm until the end;" we need to "take care" that we do not, by an unbelieving heart "fall away from the living God;" we need to not follow an example of "disobedience" (Hebrews 3:12, 14, 18-19; 4:11). And, lest we think that we have anything in and of ourselves about which to boast, we must always remember that, as did Abraham and all the great "cloud of witnesses" before us, we too should "work out [our] salvation with fear and trembling; for it is God who is at work in [us], both to will and to work for His good pleasure" (Hebrews 12:1; Philippians 2:12-13). This second aspect, which itself has primacy, can never be forgotten when we consider the importance of the former part. Everything in our life as Christians - belief, initial salvation, love for God, sanctification, obedience, steadfastness, faithfulness, holiness, etc. - is recursively dependent and saturated with God's grace and mercy.