In the first place, we should learn the folly of man’s trying to fulfill the promises of God. God had promised to Abraham an innumerable seed. When the promise was made, it was beyond all human possibility that Abraham should have a son by his wife, but he accepted the word of the Lord, and his faith was counted to him for righteousness. This in itself was evidence that the seed was not to be an ordinary seed, but that it was to be a seed of faith. EVCO 75.1
But his wife had not the faith that he had. Yet she thought that she had faith, and even Abraham doubtless thought that in carrying out her advice he was working in harmony with the word of the Lord. The mistake was in harkening to the voice of his wife, instead of to the Lord. They reasoned that God had promised them a large family, but that since it was impossible for her to have children, it was very evident that He intended that they should devise some other means of bringing it about. Thus it is that human reason deals with the promises of God. EVCO 75.2