Genesis 18:12

Therefore Sarah laughed within herself
Not for joy of a son, and as pleased with it, believing so it would be; but as disbelieving it, and perhaps deriding it, and confuting it with a laugh, which, though it did not appear in her countenance, was secretly in her heart: saying,
not with her mouth, but in her mind, after I am waxed old,
being almost ninety years of age, shall I have pleasure?
in conception, or rather in having a son, and in suckling and nursing him, and bringing him up; for in bearing and bringing forth is sorrow: and my Lord being old also;
which increased the difficulty and her unbelief: the Apostle Peter seems to have respect to this in ( 1 Peter 3:6 ) .