Charles Ellicott Commentary Romans 4:18

"Who in hope believed against hope, to the end that he might become a father of many nations, according to that which had been spoken, So shall thy seed be." — Romans 4:18 (ASV)

Who.—It must be noticed that the relative here refers to Abraham, whereas in the previous verse it referred to God.

Believed in hope.—The force of the preposition gives the sentence more the meaning of “grounded his faith upon hope”—that internal, subjective hope that was strong within him, though there were no objective grounds for hoping.

That he might become.—So that by the exercise of faith he would carry out God’s purpose.