Genesis 21:7

And she said, Who would have said unto Abraham, that Sarah should have given children suck? for I have born him a son in his old age.

And she said, who would have said unto Abraham,.... No one a year ago could ever have thought of such a thing, much less have come and told Abraham that he should have a child or children by Sarah; the thing was incredible, and next to impossible; none but God himself, or an angel from him, could have declared this, as none but he could bring it about, the thing is so marvellous and astonishing:

that Sarah should have given children suck? that she who was ninety years of age should bear a child, and suckle it, as she did; and in doing which she set an example to her daughters to do the like, since neither age nor grandeur, nor the business of her family, were any objection to this duty of nature; and her being able to do this was a clear proof that this was truly a child of her own. The plural number may be put for the singular, as it often is, see Genesis 46:23; or Sarah might think, as she had strength given her to bear and suckle one child, she might bear and suckle more; though the phrase seems only to be expressive and descriptive of her as a nursing mother:

for I have borne him a son in his old age; See Gill on "Genesis 21:2".