Genesis 18:9 - Joseph Benson’s Commentary on the Old and New Testaments

Where is Sarah thy wife? By naming her, they gave intimation to Abraham, that though they seemed strangers, yet they well knew him and his family: by inquiring after her, they showed a kind concern for the family of one whom they found respectful to them. And by speaking of her, she overhearing it, they drew her to listen to what was further to be said.