Romans 4:18-21

Verse 18

Who 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.
Verse 19

He considered not his own body now dead - He showed at once the correctness and energy of his faith: God cannot lie; Abraham can believe. It is true that, according to the course of nature, he and Sarah are so old that they cannot have children; but God is almighty, and can do whatsoever he will, and will fulfill his promise. This was certainly a wonderful degree of faith; as the promise stated that it was in his posterity that all the nations of the earth were to be blessed; that he had, as yet, no child by Sarah; that he was 100 years old; that Sarah was 90; and that, added to the utter improbability of her bearing at that age, she had ever been barren before. All these were so many reasons why he should not credit the promise; yet he believed; therefore it might be well said, Rom 4:20, that he staggered not at the promise, though every thing was unnatural and improbable; but he was strong in faith, and, by this almost inimitable confidence, gave glory to God. It was to God's honor that his servant put such unlimited confidence in him; and he put this confidence in him on the rational ground that God was fully able to perform what he had promised.
Verse 21

And being fully persuaded - πληροφορηθεις, his measure: his soul was full of confidence, that the truth of God bound him to fulfill his promise and his power enabled him to do it.
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