Abraham’s true son shares Abraham’s faith. He trusts Abraham’s God. As we survey Abraham’s life, we observe the birth of Isaac according to God’s promise came 25 years after God gave the promise when he was 100 years old. Although Abraham had other children until then and after that, Isaac would inherit all the spiritual promises that God gave Abraham. Isaac would be the son by whom Messiah would come. He was the fulfilment of God’s promise to Abraham. A child that came at Sarah’s old age, way past the age of child-bearing.