2139. That the Rational was to be made Divine is meant by the son whom Sarah was to bear, verse 9. That merely human rational truth present within the Lord did not perceive this and so did not believe it is meant by Sarah's laughing 'at the tent door which was behind him', verses 10-13, 15. It is confirmed that the Lord would cast this off as well and would take on Divine truth in place of it, verse 14.