Look unto Abraham your father, and unto Sarah that bare you… – Isaiah 51:2

The text says, “Look unto Abraham your father, and unto Sarah that bare you,” and it must mean, “consider him and see what he was, that you may learn from him.” You perceive at once that his grand characteristic was his faith. In this faith many other most brilliant qualities are comprehended, but his faith lay at the bottom of all. Here is his epitaph: “Abraham believed God.” That was a mainspring of all his acts, the glory of his life, “Abraham believed God.” The men that God will work by, whatever else they have not, must have faith in God. Though it is to be desired that the believer should have every mental and moral qualification, yet it is astounding how, if there be real faith, a multitude of imperfections are swallowed up, and the man is still a power.

The like faith also dwelt in the breast of Sarah; and, as we are told in the text to look to Sarah as well as Abraham, let us not fail to do so. The faith of Sarah was not little when she left home with her husband; forsaking her kith and kin from love to God, and to him whom she called “lord.” She acted as if she had said to the great patriarch, “Where thou goest I will go; where thou dwellest I will dwell, for thy God is my God.” Great was her faith that she never raised a question about the propriety of her husband’s course of life: and though she laughed when she was told that she should bear a son, yet remember that in the eleventh of Hebrews it is written, “Through faith also Sarah herself received strength.” She was the mother of Isaac, not in the power of the flesh, but through the energy of faith, therefore look at her as the text bids you. ~ C.H. Spurgeon

https://www.blueletterbible.org/Comm/spurgeon_charles/sermons/1596.cfm