God changed both Abraham and Sarah’s names: Abram to Abraham, and Sarai to Sarah. What is the significance of this name change? The Talmud in Berachot 13a explains that both changes share a common theme.
The name Abram means “father of Aram.” At first, Abraham was only a leader of the nation of Aram, but in end, he became a spiritual leader for the entire world. Thus, he became Avraham — “Av hamon goyim,” the father of many nations.
The name Sarai means “my princess.” In the beginning, she was only a princess for her own people. In the end, though, she became Sarah — “the princess” — the princess of the entire world.
In other words, the teachings of Abraham and Sarah were transformed from a local message to a universal one. Yet the Talmud tells us that there was a fundamental difference in these name changes. One who calls Abraham by his old name has transgressed a positive commandment. No such prohibition, however, exists for using Sarah’s old name. Why?
Rav Kook distinguished between the different approaches of these two spiritual giants. Abraham’s teachings correspond to the philosophical heritage of Judaism. He arrived at belief in the Creator through his powers of logic and reasoning, and used arguments and proofs to convince the people of his time. As Maimonides (Laws of Idolatry 1:9,13) wrote, “The people would gather around him and question him about his words, and he would explain to each one according to his capabilities, until he returned him to the way of truth.”
The Torah of Sarah, on the other hand, is more closely aligned with good deeds, proper customs, and practical mitzvot. Thus, the Midrash (Bereishit Rabbah 60:15) emphasizes the physical signs of her service of God — a cloud hovering at the entrance to the tent, a blessing in the dough, and a lamp burning from one Sabbath eve to the next.
The philosophical content of Judaism is universal in nature. Abraham’s ideals — monotheism, chesed, helping others - are relevant to all peoples. It is important that Abraham be recognized as a world figure in order to stress the universal nature of his teachings. He must be called Abraham, “the father of many nations.”
Practical mitzvot, on the other hand, serve to strengthen and consolidate the national character of the Jewish people. From Sarah, we inherited the sanctity of deed. These actions help develop the unique holiness of the Jewish people, which is required for the moral advancement of all nations. In this way, Sarah’s Torah of practical deeds encompasses both the national and universal spheres. Sarah, while “the princess” of the world, still remained “my princess,” the princess of her people.
(Gold from the Land of Israel pp. 51-52. Adapted from Ein Eyah vol. I, p. 69)