Vayera 

וירא

After Isaac was born, Sarah commented that the birth of Isaac was so joyful that anyone who heard about it would laugh with happiness. The Sages explain what type of joy other people experienced in the wake of Isaac’s birth. 

“Sarah said: God has made laughter for me; everyone who hears will laugh for me” (Genesis 21:6). If Reuben is rejoicing, why would Simeon care? Likewise, Sarah was remembered;<footnote data-num="50"/> why would others care? The reason is that at the moment that Sarah our matriarch was remembered, many barren women were remembered with her, many deaf people were cured and could hear, many blind people were cured and could see, many insane people became sane. That is why all were joyous with her. <source>(<i>Bereshit</i> <i>Rabba</i> 53) </source>