"You shall not call her name Sarai." Because "Sarai" implies [that she is a princess] to her own nation alone, but "you shall not call her name [Sarai] but Sarah" implies [a princess] to the whole entire world. And concerning her it is said, "A woman of valor is the crown of her husband" (Proverbs 12:4). And the yod that was taken from "Sarai" was divided between the two heh's: the one for Sarah, and the second for Abraham.
Why Sarai Became Sarah and the Split Letter Yod
Midrash Aggadah, Genesis 17:15
לא תקרא את שמה שרי. לפי ששרי משמע לאומתה לבד, אבל לא תקרא את שמה אלא שרה משמע לכל העולם כולו. ועליה נאמר אשת חיל עטרת בעלה (משלי יב ג). ויו"ד שלקח מן שרי חלקה לשני ההי"ן האחת לשרה, והשנית לאברהם: