1 After these things the word of the Lord came to Abram in a vision, saying, “Do not be afraid, Abram. I am your shield, your exceedingly great reward.”
2 But Abram said, “Lord God, what will You give me, seeing I go childless, and the heir of my house is Eliezer of Damascus?”
3 Then Abram said, “Look, You have given me no offspring; indeed one born in my house is my heir!”
4 And behold, the word of the Lord came to him, saying, “This one shall not be your heir, but one who will come from your own body shall be your heir.”
5 Then He brought him outside and said, “Look now toward heaven, and count the stars if you are able to number them.” And He said to him, “So shall your descendants be.”
6 And he believed in the Lord, and He accounted it to him for righteousness.
Lord God (v.2) = Adonai (Master) Jehovah (G0d)
Not only does this remarkable verse [verse 1] contain the first mention of “word,” but it also introduces for the first time in Scripture the words “vision,” “shield,” and “reward.” Even more significantly, this is the first of the great “I am’s” of Scripture. — Morris, page 323
Now [verse 6], once again we have a first mention, this time of the word “believe.” Abram “believed God and He counted [or ‘imputed’] it to him for righteousness.” Here is the great principle of true salvation, set forth for the first time in the Bible. Not by works do men attain or manifest righteousness, but by faith. Because they believe in the Word of God, He credits them with perfect righteousness and therefore enables sinful man to be made fit for the fellowship of a holy God. In this verse is also the first occurrence of “imputed” and the first occurrence of “righteousness” (except in the name “Melchizedek’; also, a similar word, though not the same, was applied to Noah, in Genesis 6:9, translated “just”). … This wonderful verse is quoted in three epistles of the New Testament (Romans 4:3; Galatians 3:6; James 2:23). — Morris, page 325
The imputation of righteousness to Abraham is here founded upon his believing in the Lord as the Quickener of the dead. It is in this character that He reveals Himself in a world where death reigns; and when a soul believes in Him as such, it is counted righteous in His sight. This necessarily shuts man out, as regards his cooperation, for what can he do in the midst of a scene of death? Can he raise the dead? Can he open the gates of the grave? Can he deliver himself from the power of death, and walk forth, in life and liberty, beyond the limits of its dreary domain? Assuredly not. Well, then, if he cannot do so, he cannot work out righteousness, nor establish himself in the relation of sonship. “God is not the God of the dead, but of the living,” and therefore, so long as a man is under the power of death, and under the dominion of sin, he can neither know the position of a son, nor the condition of righteousness. Thus, God alone can bestow the adoption of sons, and He alone can impute righteousness, and both are connected with faith in Him as the One who raised up Christ from the dead.
It is in this way that the apostle handles the question of Abraham’s faith, in Romans 4, where he says, “It was not written for his sake alone, that it was imputed onto him; but for us also, to whom it shall be imputed, if we believe on Him that raised up Jesus our Lord from the dead.” Here, the God of resurrection is presented “to us also” as the object of faith, and our faith in Him as the alone ground of our righteousness. If Abraham had looked up into heaven’s vault, spangled with innumerable stars, and then looked at “his own body now dead,” how could he ever grasp the idea of a seed as numerous as those stars? Impossible. But he did not look at his own body, but at the resurrection-power of God; and inasmuch as that was the power which was to produce the seed, we can easily see that the stars of heaven and the sand on the sea-shore are but feeble figures indeed; for what natural object could possible illustrate the effect of that power which can raise the dead?
So also, when a sinner hearkens to the glad tidings of the gospel, were he to look up to the unsullied light of the divine presence, and then look down into the unexplored depths of his own evil nature, he might well exclaim, How can I ever get thither?—how can I ever be fit to dwell in that light? Where is the answer? In himself? Nay, blessed be God, but in that blessed One who traveled from the bosom to the cross and the grave, and from thence to the throne, thus filling up, in His Person and work, all the space between those extreme points. There can be nothing higher than the bosom of God—the eternal dwelling-place of the Son, and there can be nothing lower than the cross and the grave; but, amazing truth! I find Christ in both. I find Him in the bosom, and I find Him in the grave. He went down into death in order that he might leave behind Him, in the dust thereof, the full weight of His people’s sins and iniquities. Christ in the grave exhibits the end of everything human—the end of sin—the full limit of Satan’s power. The grave of Jesus forms the grand terminus of all. But resurrection takes us beyond this terminus, and constitutes the imperishable basis on which God’s glory and man’s blessing repose forever. The moment the eye of faith rests on a risen Christ, there is a triumphant answer to every question as to sin, judgment, death, and the grave. the One who divinely met all these is alive from the dead, and has taken His seat at the right hand of the Majesty in the heavens; and not only so, but the Spirit of that risen and glorified One, in the believer, constitutes him a son. he is quickened out of the grave of Christ: as we read “And you, being dead in your sins, and the uncircumcision of your flesh, hath He quickened together with Him, having forgiven you all trespasses” (Colossians 2:13).
Hence, therefore, sonship, being founded on resurrection, stands connected with perfect justification—perfect righteousness—perfect freedom from everything which could in anywise be against us. God could not have us in His presence with sin upon us. He could not suffer a single speck or stain of sin upon His sons and daughters. The father could not have the prodigal at his table with the rags of the far country upon him. He could go forth to meet him in those rags, he could fall upon his neck and kiss him in those rags,—it was worthy and beautifully characteristic of his grace so to do; but then to seat him at his table in the rags would never do. The grace that brought the father out to the prodigal, reigns through the righteousness which brought the prodigal in to the father. It would not have been grace had the father waited for the son to deck himself in robes of his own providing, and it would not have been righteous to bring him in in his rags, but both grace and righteousness shone forth in all their respective brightness and beauty when the father went out and fell on the prodigal’s neck, but yet did not give him a seat at his table until he was clad and decked in a manner suited to that elevated and happy position. God, in Christ, has stooped to the very lowest point of man’s moral condition, that, by stopping, He might raise man to the very highest point of blessedness, in fellowship with Himself. From all this, it follows that our sonship, with all its consequent dignities and privileges, is entirely independent of us. We have just as little to do with it as Abraham’s dead body and Sarah’s dead womb had to do with a seed as numerous as the stars which garnish the heavens, or as the sand on the sea-shore. It is all of God. — Mackintosh, pages 163-166
In ratifying the promise (i.e., the “Abrahamic Covenant”), therefore, God is not “activating” it, but rather establishing the certainty of its fulfillment in the mind of Abraham—i.e., here, as continually throughout the history of redemption, God condescends to “meet” man in his lack of faith by doing more (or less, depending on one’s perspective) than required by the ideal since the depraved man that He interacts with are so far from that ideal. — Wechsler, page 186.
As in the initial expression of God’s promise in Genesis 12, so too here the scene commences immediately with God’s active expression of what He will do for Abram (and his descendants in the line of Promise). And so too here, as in the latter part of Genesis 12, God’s declaration of promise is followed by a clear expression of doubt on the part of Abram. In the present instance this doubt is represented by Abram’s questioning response, “O Lord God, what will You give me, since I am childless, and the heir of my house is Eliezer of Damascus?” By this question, in other words, Abram is, at best, seeking to “force” God’s “hand” into specifying and fulfilling His previous statement, “I will make you into a great nation” (Genesis 12:2); at worst he is rhetorically denying that God can in fact give him the son that he so desires, Sarai being barren (see Genesis 11:30) and postmenopausal to boot (see Genesis 18:13), in which latter case Abram’s statement in verse 2 should be understood as the despondent statement of an old man of little faith anticipating his death (as is perfectly consistent with the Hebrew grammar). As in chapter 12, however, God responds not with judgment, but with patience and grace, thus emphasizing the unconditional nature of His promise. — Wechsler, page 187.
[Genesis 15:6] is referring to the fact that Abraham, who is already a believer, believed even more so (but still far from perfectly; see Genesis 17:17) in God’s specific promise of an heir, and this inner “act” of expressing greater faith was therefore credited to Abraham as a specific act of righteousness (thus yielding an added “notch” to his reward in the hereafter). … This is absolutely consistent with Paul’s citation of this verse in Romans 4, the point of which chapter is, simply, that righteousness is based first and foremost on faith (i.e., the inner “acts” or affirmations, of one’s heart)—whether that be one’s initial faith in Christ as the resurrected Lord, resulting in the overall righteousness of justification, or (as in the present instance) the believer’s subsequent and growing faith in the specific promises and commands of God’s Word, as reflected in the righteous acts that he performs in obedience to those promises and commands. — Wechsler, pages 188-189.