Abraham's two sons are declared by Paul to be the types of two races of men, who are much alike, and yet widely differ. They are unlike in their origin. They were both sons of Abraham; but Ishmael, the child of Hagar, was the offspring of Abraham upon ordinary conditions: he was born after the flesh. Isaac, the son of Sarah, was not born by the strength of nature; for his father was more than a hundred years old, and his mother was long past age. He was given to his parents by the Lord, and was born according to the promise through faith. This is a serious distinction, and it marks off the true child of God from him who is only so by profession. The promise lies at the bottom of the distinction, and the power which goes to accomplish the promise creates and maintains the difference. Hence the promise, which is our inheritance, is also our test and touchstone.