Heb 11:8-10 poses problems for Reformed theology, especially for those who believe that Abraham’s once and for all justification took place at Gen 15:6, as Heb 11, speaking of events in Gen 12, ascribes “saving/true faith” to Abraham, and contrary to James White and others, Abraham does have an object of faith. For more on Gen 15:6 and how Protestants are guilty of eisegesis of this text, see:
Matthew Poole, a 17th-century Reformed theologian, offered the following commentary on Heb 11:8-12. Do note how his comments assume that Abraham had true saving faith in Gen 12 as well as Saras (in vv. 11-12):
8 By faith Abraham, when he was called to go out into a place which he should after receive for an inheritance, obeyed; and he went out, not knowing where he went.
Here begin instances of this Divine faith after the flood from Abraham to Moses’s time, ver. 8-32. The first is the father of believers, to entitled by God, eminent in the exercise of this grace, of whose ancestry, and their descent from him, these Hebrews did greatly glory. He had an express discovery of the will of God unto him, that he should leave the idolatrous place where he lived, Gen. xi. 31; xii. 1-3; compare Josh. xxiv.2; Acts vii. 2, 3; and with his family should travel to a land which God would show him, and which he would give him as an inheritance for him and his, which was the land of Canaan, as described, Gen. xiii.14-17; xxv. 18, 19, 21. This command of God, strengthened by a promise, he obeyed, Gen. xii. 4; Acts vii.4: through faith, really, freely, and fully designing up himself and his to God’s disposal. And he went out not knowing whither he went; he went forth with his father Terah from his country, kindred, and friends, in Ur of the Chaldees, to Charran, and there they dwelt till Terah died, Gen. xi. 31; Acts vii. 4. After which, he pursued God’s orders in his motion from place to place, though he knew neither the way, nor the place in which and whither he was to move, resting himself on God’s word and guidance, and relying wholly on his provision for him, and protection of him in all his ways.
9 By faith he sojourned in the land of promise, as in a strange country, dwelling in the tabernacles with Isaac and Jacob, the heirs with him of the same promise:
By faith he sojourned in the land of promise as in a strange country; by the same Divine faith he passed from tent to tent, moving it from place to place, as God ordered; so as he rather sojourned than dwelt in any. His journal is legible in Moses’s history, moving from Charran to Shechem, from thence to Beth-el, and then more southward, and thence to Egypt; see Gen. xii.: so that he sojourned in Canaan, and the adjoining countries, which God had covenanted to give for an inheritance to him and his seed, Gen. xv.18-21; yet by faith he would stay God’s time for it, but lived in it as a stranger, not having in possession one foot of ground, but what he bought for a burying-place, Gen. xxv. 9, 10; Acts vii. 5. Dwelling in tabernacles with Isaac and Jacob, the heirs with him of the same promise: here he, with his son Isaac, and grandson, and their seed, coheirs with him of Canaan, built no house, but lived in tents, which they might pitch or remove at God’s pleasure, and as he called them, as who were strangers to this country, and to the inhabitants of it, with whom they were to have no spiritual society, as travelling to a better; being in this world, but neither citizens nor inhabitants of it, but as denizens of a more excellent one, Gen. xxvi. 3; xxviii. 13, 14.
10 For he looked for a city which hath foundations, whose builder and maker is God.
The reason for this contented pilgrimage was the excellent end of it, the place and state to which it brought him; he did really discern by the Spirit’s work in him, and promise to him, his title to it, and vehemently did desire and long for, and yet patiently waited for, a better place and state than this earthly; and was daily making his approaches to it, Rom. viii.19; 2 Cor. v. 1, 2, 8, 9. For he looked for a city which hath foundations: πολις notes both a place made up and constituted of buildings and houses, such was the earthly Jerusalem; and a state, polity, or community. Here it must be understood spiritually, for such a place and state as is not to be shadowed out by any in this world; no earthly can decipher, or set out. This city is heaven itself, often so styled in this Epistle, as ver. 16; chap. xii. 22; xiii. 14; Rev. iii. 12. It is not movable, as a tent fastened by stakes and cords not as creature-buildings, perishable. Histories tell us of the rise and fall of the best earthly cities; this city is built on the Rock of ages, as well as by him, whose immutability, almightiness, and eternity hath laid and settled its foundations, the basis and ground-work, firm and incorruptible, 1 Pet. i.4. Whose builder and maker is God; the happy fabric, with persons and state endures for ever, because of its Raiser and Founder. The great Architect, that cast the plot and model of it in his own mind , and the publicly-declared Operator and Raiser of it, who laid the foundations, reared the mansions, and finished the whole, is no less person than the infinitely wise, almighty, and eternal God. It all became him alone, and doth as far exceed other cities as God doth men. No human art or power was fit or capable for such a work, but only God.
11 Through faith also Sarah herself received strength to conceive seed, and was delivered of a child when she was past age, because she judged him faithful who had promised.
Through faith also Sarah herself received strength to conceive seed; by the same Divine faith in Abraham and Sarah was brought forth the child of promise. For though the instance be expressly in Sarah, yet it is inclusive of Abraham also, who was eminent for his faith in this thing, acquiring an eminent title by it, even of the Father of believers, as the apostle declareth, Rom. iv.17-22, and therefore jointly to be considered with Sarah. She, who first through unbelief laughed at the promise, yet being reproved by Christ, the Angel of the covenant, for it, believed on the repetition of it. Gen. xviii.9-16, and gave testimony of it by her waiting for the promise mercy. As barren as she was, yet faith made her faithful; when it was impossible of herself to expect it for nature or years, yet to conceive seed, that is, laying the foundation of it, conceiving in her dead womb, and bearing a son. And was delivered of a child when she was past age; she was not just only naturally barren, but of ninety years of age at this time, when the most fruitful were past such work; yet by faith as he was the son of promise, Gen. xv. 4; xviii. 11; compare Rom. iv. 17-19. Because she judged him faithful who had promised; she gave glory to God by a firm and hearty closure with his promise, accounting God faithful to his word, and able to perform it, and so rested on it, and waited for him, as Abraham did, Rom. iv. 18, 20, 21. The promise which he made was, That they in their old age should have a son, Gen. xii. 2; made in general chap. xiii. 15, 16; in particular, chap. xv. 4, 5; to both, chap. xvii. 15-17; xviii. 10, 14; xxi. 1-3, 12.
12 Therefore sprang there even of one, and him as good as dead, so many as the stars of the sky in multitude, and as the sand which is by the sea shore innumerable.
Because of this faith Abraham and Sarah, and the fruit of it in conceiving and bringing forth Isaac, was laid the foundation of a numerous seed by God’s promise; from Abraham, a hundred, and Sarah, ninety years old, and barren, and both dead as to procreation, Rom. iv. 9, there were begotten a vast and unbounded seed, as the stars in the firmament or the sand on the seashore; and amongst them the teeming blessing, the one eminent Seed of Abraham, the Messiah, in whom all nations were to be blessed. Within four hundred years from the birth of Isaac, this seed increased to above six hundred thousand fighting men, besides women and children, and after increased to a stupendous greatness according to the promise, Gen. xiii. 16; xv. 5; Exod. xii. 47; 1 Chron. xxi. 5, 6. (Matthew Poole, A Commentary on the Holy Bible, volume 3: The New Testament [1685; repr., Edinburgh: The Banner of Truth Trust, 1963, 1990], 861-62)