For we are made partakers, etc. He commends them for having begun well; but lest, under the pretext of the grace which they had obtained, they should indulge themselves in carnal security, he says that there was need of perseverance; for many having only tasted the Gospel, do not think of any progress as though they had reached the summit. Thus it is that they not only stop in the middle of their race, yea, nigh the startingposts, but turn another way. Plausible indeed is this objection, "What can we wish more after having found Christ?" But if he is possessed by faith, we must persevere in it, so that he may be our perpetual possession. Christ then has given himself to be enjoyed by us on this condition, that by the same faith by which we have been admitted into a participation of him, we are to preserve so great a blessing even to death. [1] Hence he says beginning, intimating that their faith was only begun. As hypostasis sometimes means confidence, it may be so taken here; yet the term substance, as some have rendered it, I do not dislike, though I explain it in a way somewhat different. They think that faith is thus called, because the whole of what man may have without it is nothing but vanity; but I so regard it, because we recumb on it alone, as there is no other support on which we can rely. And suitable to this view is the word steadfast or firm; for we shall be firmly fixed and beyond the danger of vacillating, provided faith be our foundation. The sum of the whole then is, that faith whose beginnings only appear in us, is to make constant and steady progress to the end. [2]

Footnotes

1 - What is implied here is that we may professedly be partakers of Christ: that is of his blessings as a Savior, and yet be not really so: the proof of the reality is perseverance. -- Ed.

2 - Here is another instance of the genitive being the main subject, "the beginning of our confidence," i.e., our first confidence, which the Apostle calls "first faith" in 1-Timothy 5:12. Macknight renders it "the begun confidence." -- Ed.

For we are made partakers of Christ - We are spiritually united to the Saviour. We become one with him. We partake of his spirit and his allotments. The sacred writers are accustomed to describe the Christian as being closely united to the Saviour, and as being one with him see the John 15:1-7; John 17:21, John 17:23 notes; Ephesians 5:30 note; 1-Corinthians 12:27 note. The idea is, that we participate in all that pertains to him. It is a union of feeling and affection; a union of principle and of congeniality; a union of dependence as well as love; a union where nothing is to be imparted by us, but everything gained; and a union, therefore, on the part of the Redeemer of great condescension. It is the union of the branch to the vine, where the branch is supported and nourished by the vine, and not the union of the ivy and the oak, where the ivy has its own roots, and merely clings around the oak and climbs up upon it. What else can be said so honorable of man as that he is a "partaker of Christ;" that he shares his feelings here, and that he is to share his honors in a brighter world? Compared with this, what is it to participate with the rich and the frivolous in their pleasures; what would it be to share in the honors of conquerors and kings?
μετοχοι του Χριστου metochoi tou Christou cannot signify, as some explain, participation merely in the blessings of Christ's death, but must be referred, as our author here affirms, to the spiritual union which subsists between Christ and his people. That union doubtless involves, as necessary consequents, "a union of feeling and affection, a union of principle and congeniality, a union of dependence and love." Yet, we think, it is something more. It is a "real" and vital union, formed by the one Spirit of Christ, pervading the head and the members of the mystical body. And this is the "foundation" of all union of affection, etc. For a condensed view of the subject, see the supplementary note on Romans 8:10.)
If we hold the beginning of our confidence steadfast - see the note at Hebrews 3:6. If we continue to maintain the same confidence which we had in the beginning, or which we showed at the commencement of our Christian life. At first, they had been firm in the Christian hope. They evinced true and strong attachment to the Redeemer. They were ardent and devoted to his cause. If they continued to maintain that to the end, that is, the end of life; if in the midst of all temptations and trials they adhered inflexibly to the cause of the Saviour, they would show that they were true Christians, and would partake of the blessedness of the heavenly world with the Redeemer. The idea is, that it is only perseverance in the ways of religion that constitutes certain evidence of piety. Where piety is manifested through life, or where there is an untiring devotion to the cause of God, there the evidence is clear and undoubted.
But where there is at first great ardor, zeal, and confidence, which soon dies away, then it is clear that they never had any real attachment to him and his cause. It may be remarked here, that the "beginning of the confidence" of those who are deceived, and who know nothing about religion at heart, is often as bold as where there is true piety. The hypocrite makes up in ardor what he lacks in sincerity; and he who is really deceived, is usually deceived under the influence of some strong and vivid emotion, which he mistakes for true religion. Often the sincere convert is calm, though decided, and sometimes is even timorous and doubting; while the self-deceiver is noisy in profession, and clamorous in his zeal, and much disposed to blame the lukewarmness of others. Evidence of piety, therefore, should not be built on that early zeal; nor should it be concluded that because there is ardor, there is of necessity genuine religion. Ardor is valuable, and true religion is ardent; but there is other ardor than what the gospel inspires. The evidence of genuine piety is to be found in what will bear us up under trials, and endure amidst persecution and opposition. The doctrine here is, that it is necessary to persevere if we would have the evidence of true piety. This doctrine is taught everywhere in the Scriptures. Persevere in what? I answer, not:
(1) merely in a profession of religion. A man may do that and have no piety.
(2) not in zeal for party, or sect. The Pharisees had that to the end of their lives.
(3) not in mere honesty, and correctness of external deportment. A man may do that in the church, as well as out of it, and yet have no religion.
But we should persevere:
(1) in the love of God and of Christ - in conscious, ardent, steady attachment to Him to whom our lives are professedly devoted.
(2) in the secret duties of religion. In that watchfulness over the heart; that communion with God; that careful study of the Bible; that guardianship over the temper; and in that habitual contact with God in secret prayer which is appropriate to a Christian, and which marks the Christian character.
(3) in the performance of the public duties of religion; in leading a "Christian" life - as distinguished from a life of worldliness and vanity; a life of mere morality, and honesty; a life such as thousands lead who are out of the church.
There is something which distinguishes a Christian from one who is not a Christian; a religious from an irreligious man. There is "something" in religion; "something" which serves to characterize a Christian, and unless that something is manifested, there can be no evidence of true piety. The Christian is to be distinguished in temper, feeling, deportment, aims, plans, from the people of this world - and unless those characteristics are shown in the life and deportment, there can be no well-founded evidence of religion.
Learn:
(1) that it is not mere "feeling" that furnishes evidence of religion.
(2) that it is not mere "excitement" that constitutes religion.
(3) that it is not mere ardor.
(4) that it is not mere zeal.
All these may be temporary. Religion is something that lasts throughout life. It goes with a person everywhere. It is with him in trial. It forms his plans; regulates his temper; suggests his words; prompts to his actions. It lives with him in all his external changes, and goes with him through the dark valley of death, and accompanies him up to the bar of God, and is with him forever.

For we are made partakers of Christ - Having believed in Christ as the promised Messiah, and embraced the whole Christian system, they were consequently made partakers of all its benefits in this life, and entitled to the fulfillment of all its exceeding great and precious promises relative to the glories of the eternal world. The former they actually possessed, the latter they could have only in case of their perseverance; therefore the apostle says, If we hold fast the beginning of our confidence steadfast unto the end, i.e. of our life. For our participation of glory depends on our continuing steadfast in the faith, to the end of our Christian race.
The word ὑποστασις, which we here translate confidence, from ὑπο, under, and ἱστημι, to place or stand, signifies properly a basis or foundation; that on which something else is builded, and by which it is supported. Their faith in Christ Jesus was this hypostasis or foundation; on that all their peace, comfort, and salvation were builded. If this were not held fast to the end, Christ, in his saving influences, could not be held fast; and no Christ, no heaven. He who has Christ in him, has the well-founded hope of glory; and he who is found in the great day with Christ in his heart, will have an abundant entrance into eternal glory.

(8) For we are made partakers of Christ, if we hold the (k) beginning of our confidence stedfast unto the end;
(8) Now he considers these words, "If you hear his voice" showing that they are spoken and meant of the hearing of faith, opposite which he places hardening through unbelief.
(k) That beginning of trust and confidence: in the speech of the Hebrews, he calls "beginning" that which is chiefest.

For we are made partakers of Christ,.... Being loved by him, given to him, and chosen in him before the foundation of the world; and so participate of all spiritual blessings in him; for this respects something past, and may be rendered, "we have been made". The phrase is expressive of union to Christ, which is not by faith on man's part, and by the Spirit on Christ's part, but by his everlasting love, taking his people into an oneness with himself; thereby becoming their head, surety, and representative, which is the ground and foundation of all the blessings of grace being imparted to them: hence arises communion; as this is a conjugal union, there is communion of names, of persons, of goods, of honour and dignity, and of everlasting glory; as it is a federal or representative union, hence a non-imputation of sin, justification, and freedom from condemnation; and as it is an union of head and members; hence a communication of life, and the security of it, and of all grace and strength; hence holiness, fruitfulness, and perseverance, and everlasting happiness both of soul and body:
if we hold fast the beginning of our confidence steadfast unto the end; by "confidence" is meant faith, which is an hypostasis, or subsistence, which is the word here used; and is so called, because it gives a kind of subsistence, substance, or being, to things it is concerned with, Hebrews 11:1 and because it is a great support to believers, under their various exercises; and is that by which they have an open, spiritual, and comfortable subsistence, and abiding in Christ: the "beginning" of it, which is to be held fast, is either Christ himself, who is the "the beginning", the author, and finisher of faith; and so this shows from whom, and in what way, this grace is distributed; and is expressive of communion with Christ, and is an evidence of the participation of him: or else the Gospel, which is the means of implanting faith, and directs to that which is the ground and foundation of it; and this is to be held fast, and never to be departed from: or else the grace of faith itself, which is a grace but begun, not yet finished, but shall continue, and is to be held fast, and constantly exercised; and perseverance in believing on Christ is an evidence of union to him.

The saints' privilege is, they are made partakers of Christ, that is, of the Spirit, the nature, graces, righteousness, and life of Christ; they are interested in all Christ is, in all he has done, or will do. The same spirit with which Christians set out in the ways of God, they should maintain unto the end. Perseverance in faith is the best evidence of the sincerity of our faith. Hearing the word often is a means of salvation, yet, if not hearkened to, it will expose more to the Divine wrath. The happiness of being partakers of Christ and his complete salvation, and the fear of God's wrath and eternal misery, should stir us up to persevere in the life of obedient faith. Let us beware of trusting to outward privileges or professions, and pray to be numbered with the true believers who enter heaven, when all others fail because of unbelief. As our obedience follows according to the power of our faith, so our sins and want of care are according to the prevailing of unbelief in us.

For, &c.--enforcing the warning, Hebrews 3:12.
partakers of Christ--(Compare Hebrews 3:1, Hebrews 3:6). So "partakers of the Holy Ghost" (Hebrews 6:4).
hold--Greek, "hold fast."
the beginning of our confidence--that is, the confidence (literally, substantial, solid confidence) of faith which we have begun (Hebrews 6:11; Hebrews 12:2). A Christian so long as he is not made perfect, considers himself as a beginner [BENGEL].
unto the end--unto the coming of Christ (Hebrews 12:2).

For we are made partakers of Christ - And we shall still partake of him and all his benefits, if we hold fast our faith unto the end. If - But not else; and a supposition made by the Holy Ghost is equal to the, strongest assertion. Both the sentiment and the manner of expression are the same as Hebrews 3:6.