The Laughter of Abraham
When God announces to Sarah that she would give birth to a son, “Sarah laughed to herself” (Genesis 18:12), whereas earlier when Abraham was first told of the miracle son, he “fell on his face and laughed” (Genesis 17:17).
Sarah is rebuked, whereas Abraham isn’t, for their laughter. Why? Because Sarah is laughing “to herself” at God’s promise. It was laughter of enclosure in self. It was not a shared laughter, but a laughter of disbelief.
Whereas Abraham laughs not to himself but to God, since falling on your face is a gesture of submission. We can assume the laughter was not that of unbelief, which would have earned him a rebuke. He was worshipping. You cannot worship God and disbelieve him at the same time. Abraham’s was a special laughter unique to God’s people: the laughter of joy and delight and wonder that only God can evoke in us by his extravagance and chutzpah.
In support of this reading, Romans 4:20 relates that Abraham “staggered not” at God’s promise; we also learn that Sarah repented of her unbelief, as she is roundly praised in the gallery of heroes (Hebrews 11:11).
It is usually taught that Abraham was laughing in disbelief, like Sarah. Scholars disagree on this point. But in the school of Christ, different readings can exist side-by-side without a problem, just as a man and a woman can exist side-by-side. So we say that Sarah’s laughter is unbelief, but Abraham’s is laughter of baffled wonder at Abba’s outrageous sense of humour.