On the day Isaac was weaned, Abraham threw open his tents and invited every household in the land. It was meant as a celebration, but rumor crawled in with the guests. Whispers passed around the cups: "This old couple adopted a foundling. They invite us so we will swear the child is theirs."
Abraham had anticipated the slander. He invited every notable in the region, and Sarah invited their wives. She asked the women to come without wet nurses and to bring their infants directly. When the feast began, Sarah's breasts became like two fountains, and she nursed every child in the tent from her own body. One after another, babies who did not belong to her suckled and were full.
Still some guests held out. "Shall a child truly be born to a man a hundred years old?" they murmured. "Shall a woman of ninety bear?" (Genesis 17:17).
At that moment, Isaac's face shifted before their eyes. Feature by feature, the infant took on the exact likeness of Abraham. The room fell quiet. Then, as one, the guests declared, "Abraham begat Isaac." (Bava Metzia 87a).
A miracle, the sages teach, is sometimes the only answer the world will accept.