18 who, contrary to hope, in hope believed, so that he became the father of many nations, according to what was spoken, “So shall your descendants be.”
Old Abraham and Sarah had no hope on a human level of having a child, but there was another dimension in their lives that gave them hope.
18 who [Abraham], contrary to hope,
It was not reasonable for Abraham and Sarah to hope for a child in their old age. There was no ground for believing that they would have a child. Against any substantive human reason, Abraham believed. This is an oxymoron, the combination of opposing ideas. There was a divine ground for his hope but no human ground or expectation for it.
Paul used the word “hope” more than anyone else in the New Testament. He used the word in Romans more than any other book.
in hope believed,
Note the contrast between “contrary to hope” (against all hope) and “in hope.” Abraham believed what God promised, what He said.
This is the second use of “believed” in two verses (cf. v.17). This echoes Genesis 15:6 used earlier in the chapter, where Abraham exercised his faith.
The hope in this phrase is determined by God’s promise to Abraham. “Hope” in the English carries the idea of uncertainty of an unknown future or expectation. Biblically, hope expects the good; even more, it is confident that the good will happen. There is a trust dimension to hope; there is confidence in God in the exercise of hope. Abraham’s faith expressed itself in confidence in his God as the One who would provide a son even in the face of human skepticism about it happening.
so that he became the father [ancestor] of many nations,
God did what He did in waiting till Abraham was old to demonstrate how he would bring about his fatherhood of “many nations” by faith (Ge 17:5). He wanted Abraham to believe in the face of the great obstacle of old age.
according to what was spoken,
Paul quoted Genesis 15:5.
“So shall your descendants be.”
Abraham’s fatherhood over all nations was God’s intention from the start, from the book of Genesis. This was the fulfillment of Abraham’s hope. Against the idea that Abraham would have even one son, he became the father of nations.
Biblical hope is confidence in God’s promises by faith.
Biblical hope is more than optimism because it grounds in confidence in God’s promises. That is why the Bible often links hope with faith. Often there is nothing to justify our hope as Christians other than God’s promise. Hope is bound up with faith in God. True faith is strong and consistent in opposition to appearances otherwise. It has the capacity to see beyond circumstance. There are many symptoms that challenge the promises of God. Faith is unreasonable only to those who deny God’s intervention into the world.
The hope of the New Testament is a hope of certainty. We believe in the hope (confidence) that God will do what He promises. This hope is not the hope of the indomitable human spirit rising up against all odds. There is nothing invincible in man.