Abraham believed in the Lord; and he counted it to him for righteousness. -- GEN.15:6.

He staggered not at the promise of God through unbelief; but was strong in faith, giving glory to God; and being fully persuaded that, what he had promised, he was able also to perform. And therefore it was imputed to him for righteousness. Now it was not written for his sake alone, that it was imputed to 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.

The promise, that he should be the heir of the world, was not to Abraham, or to his seed, through the law, but through the righteousness of faith.

The just shall live by faith. -- Let us hold fast the profession of our faith without wavering; (for he is faithful that promised). -- Our God is in the heavens; he hath done whatsoever he hath pleased. -- With God nothing shall be impossible. And blessed is she that believed: for there shall be a performance of those things which were told her from the Lord.

Rom.4:20-24.Rom.4:13.Rom.1:17. -Heb.10:23. -Psa.115:3. -Luke 1:37,45.