John Calvin's Commentary on the Bible - Genesis 18:12
Verse 12 12.Therefore Sarah laughed within herself Abraham had laughed before, as appears in the preceding chapter Genesis 17:1 : but the laughter of both was, by no means, similar. For Sarah is not transported with admiration and joy, on receiving the promise of God; but foolishly sets her own age and that of her husband in opposition to the word of God; that she may withhold confidence from God, when he speaks. Yet she does not, avowedly, charge God with falsehood or vanity; but because,... read more
John Calvin's Commentary on the Bible - Genesis 18:11
Verse 11 11.Were old, and well stricken in age Moses inserts this verse to inform us that what the angel was saying, justly appeared improbable to Sarah. For it is contrary to nature that children should be promised to decrepit old men. A doubt, however, may be entertained on this point, respecting Abraham: because men are sometimes endued with strength to have children, even in extreme old age: and especially in that period, such an occurrence was not uncommon. But Moses here speaks... read more