| Barnes' Notes on the Bible Who against hope - Who against all apparent or usual ground of hope. He refers here to the prospect of a posterity; see Romans 4:19-21. Believed in hope - Believed in what was promised to excite his hope. Hope here is put for the object of his hope - what was promised. According to what was spoken - Genesis 15:5. So shall thy seed be - That is, as the stars in heaven for multitude. Thy posterity shall be very numerous.
Clarke's Commentary on the BibleWho against hope believed in hope - The faith of Abraham bore an exact correspondence to the power and never-failing faithfulness of God; for though, in the ordinary course of things, he had not the best foundation of hope, yet he believed that he should be the father of many nations, according to that which was spoken; namely, that his posterity should be like the stars of heaven for multitude, and like the dust of the earth.
Gill's Exposition of the Entire BibleWho against hope believed in hope,.... Abraham believed the promise of God, that he might become the father of many nations, being assisted by a supernatural aid: "in hope"; of the fulfilment of it by the grace and power of God: "against hope": against all visible, rational grounds of hope; Sarah's womb and his own body being dead, but inasmuch as God had said it, he believed: according to that which is spoken, so shall thy seed be; his faith rested upon the word of God, which showed the nature of it, and that it was of the right kind.
Geneva Study Bible{17} Who against hope believed in hope, that he might become the father of many nations, according to that which was spoken, So shall thy seed be. (17) A description of true faith wholly resting in the power of God, and his good will, set forth in the example of Abraham.
People's New Testament 4:18 Who against hope. Though an old man, and his wife an aged woman, far beyond the time of child-bearing, he yet believed the promise that he would have numerous offspring.
Wesley's Notes 4:18-21 The Apostle shows the power and excellence of that faith to which he ascribes justification. Who against hope - Against all probability, believed and hoped in the promise. The same thing is apprehended both by faith and hope; by faith, as a thing which God has spoken; by hope, as a good thing which God has promised to us. So shall thy seed be - Both natural and spiritual, as the stars of heaven for multitude. Gen 15:5.
Jamieson-Fausset-Brown Bible Commentary18-22. Who against hope-when no ground for hope appeared. believed in hope-that is, cherished the believing expectation. that he might become the father of many nations, according to that which was spoken, So shall thy seed be-that is, Such "as the stars of heaven," Ge 15:5.
Matthew Henry's Concise Commentary4:13-22 The promise was made to Abraham long before the law. It points at Christ, and it refers to the promise, Ge 12:3. In Thee shall all families of the earth be blessed. The law worketh wrath, by showing that every transgressor is exposed to the Divine displeasure. As God intended to give men a title to the promised blessings, so he appointed it to be by faith, that it might be wholly of grace, to make it sure to all who were of the like precious faith with Abraham, whether Jews or Gentiles, in all ages. The justification and salvation of sinners, the taking to himself the Gentiles who had not been a people, were a gracious calling of things which are not, as though they were; and this giving a being to things that were not, proves the almighty power of God. The nature and power of Abraham's faith are shown. He believed God's testimony, and looked for the performance of his promise, firmly hoping when the case seemed hopeless. It is weakness of faith, that makes a man lie poring on the difficulties in the way of a promise. Abraham took it not for a point that would admit of argument or debate. Unbelief is at the bottom of all our staggerings at God's promises. The strength of faith appeared in its victory over fears. God honours faith; and great faith honours God. It was imputed to him for righteousness. Faith is a grace that of all others gives glory to God. Faith clearly is the instrument by which we receive the righteousness of God, the redemption which is by Christ; and that which is the instrument whereby we take or receive it, cannot be the thing itself, nor can it be the gift thereby taken and received. Abraham's faith did not justify him by its own merit or value, but as giving him a part in Christ. | 
