Tosefta zu Bereschit 17:15

Similar to this [it says]: “Sarai, your wife, will not be called Sarai anymore, because her [new] name is Sarah.” (Genesis 17:15) In the beginning, she was a princess over her nation, [but] now she became a princess for all of the nations of the world, as it is said: “…because her [new] name is Sarah.” Similar to this [it says]: “And your name will not be called anymore Avram, but rather your name will be Avraham…” (Genesis 17:5) In the beginning, you were a father to Aram and now you will be a father to all people of the world, as it is said: “… because I have made you a father of a multitude of nations”.(ibid)