Therefore it is of faith, that it might be by grace; to the end the promise might be sure to all the seed; not to that only which is of the law, but to that also which is of the faith of Abraham; who is the father of us all, (As it is written, I have made thee a father of many nations,) before Him whom he believed, even God, who quickeneth the dead, and calleth those things which be not as though they were. – Romans 4:16,17
Abraham’s faith consisted in believing the promise of God and this he did firmly and practically…God promised to give him a seed and yet he had no children. Year followed year and in the course of nature he grew old and his wife was long past the age of child-bearing—and yet there was no son born to them. When at last Ishmael was born, his hope in that direction was dashed to the ground, for he was informed that the Covenant was not with Ishmael—believing Abraham had stepped aside to carnal expediency and had hoped, in that way, to realize the lingering promise! But he had 14 more years to wait—till he was 100 years old and till Sarah had reached her 90th year! Yet he believed the word of the Lord and fell upon his face and laughed with holy joy and said in his heart, “Shall a child be born unto him that is 100 years old?” So, too, when Isaac was born and grown up, he believed that in Isaac should the Covenant be established.
Now consider that we have multiplied promises and those are written down in black and white in the Inspired Word, which we may consult at any time we please, while Abraham had only, now and then, a verbal promise—and yet he clung to it and relied upon it. Though there was nothing else to rely upon and neither sign nor evidence of any offspring to fulfill the promise that he should be heir of the world and father of many nations, yet he needed no other ground of confidence but that God had said it and that He would make His word good.
He Hath Said 