(4) “As for Me, this is My covenant with you: You shall be the father of a multitude of nations. (5) And you shall no longer be called Abram, but your name shall be Abraham, for I make you the father of a multitude of nations.

כי אב המון גוים FOR A FATHER OF A MULTIDUDE OF NATIONS — An acrostic on his name [אב (ר) הם]. But the ר which was previously in his name — denoting that he was the father (chieftain) only of אב (א) רם] ארם] which was his native country (cf. Genesis 21:7 with verse Genesis 21:10 of the same chapter), whilst now he became father of the entire world — nevertheless was not taken out of his name. For we find also, that the 'י in Sarai’s name continued to complain to God that it had been removed from her name when this was changed to Sarah, until it was placed as an additional letter into the name יהושע, as it is said, (Numbers 13:16) “And Moses called Hoshea (הושע) the son of Nun, Joshua (יהושע)” (Genesis Rabbah 47:1).

We learned in the mishna If one wrote one letter as an abbreviation [notarikon] representing an entire word, Rabbi Yehoshua ben Beteira deems him liable to bring a sin-offering, and the Rabbis deem him exempt. Rabbi Yoḥanan said in the name of Rabbi Yosei ben Zimra: From where is it derived that the language of abbreviation is employed in the Torah? As it is stated: “Neither shall your name any more be called Abram, but your name shall be Abraham; for the father of a multitude of nations [av hamon goyim] have I made you” (Genesis 17:5). The verse itself contracts av hamon into Abraham [Avraham]. The words av hamon themselves are interpreted as an abbreviation: I have made you a father [av] for the nations, I have made you chosen [baḥur] among the nations, I have made you beloved [ḥaviv] among the nations, I have made you king [melekh] for the nations, I have made you distinguished [vatik] for the nations, I have made you trusted [ne’eman] for the nations.

"God said..., 'Sarai your wife...'" In Proverbs (12:4), it is written, "A woman of valor is a crown to her husband." Rabbi Aha said, "Her husband was crowned through her, but she was not crowned through her husband." Our rabbis taught that she ruled over her husband. In all places, the man gives orders, but here (Genesis 21:12), "In all that Sarah orders you, listen to her voice." Said Rabbi Yehoshua Ben Korcha: 'The Yud that the Holy One of Blessing took from Sarai was given half to Sarah, and half to Avraham. Said Rabbi Shime'on Bar Yochai: The Yud that the Holy One of Blessing took from Sarai flew and posted itself in front of the Throne of the Holy One, and said: 'Master of the Universe! Because I am the smallest letter You took me out of the name of Sarai the Righteous!! The Holy One said: In the past you were in the name of a woman, and in the end of the name! Now I will put you in the name of a man, and on the beginning of the name, as it is written 'And Moshe called Hosea Bin Nun Yehoshua' (Numbers 13:16). Said Rabbi Mana: Sarai was just [a princess] for herself, now she will be a princess for all the world.