Clearly, Sarah demanded Ishmael's ouster for the two reasons noted above: first, so that Isaac would not learn from his ways, and second, because it would be impossible for Ishmael not to be filled with jealousy over the land, which he saw as also belonging to him, and he would surely fight Isaac to take it away from him. [The matter greatly distressed Abraham regarding his son. So G-d said to Abraham, “Let it not be grievous in your sight because of the lad or your slave woman: Whatever Sarah tells you, heed her voice, since through Isaac will offspring be considered yours.” (Gen. 21:11-12)]. Tanchuma concludes, “from here we learn that Abraham was inferior to Sarah in prophetic powers.” Likewise, foolish, groundless love spoils the normal order of things. As Bereshit Rabbah teaches regarding Abraham's not wishing to send Ishmael away, “This belongs to 'shutting one's eyes to evil'(Isaiah 33:15)”. That is, Abraham, due to his inappropriate love, turned a blind eye to Ishmael's evil, and only Sarah saw it through her prophecy. Sarah was right in not taking the path of groundless love, and Abraham ultimately banished both Ishmael and the other concubines' sons. “Abraham gave all that he owned to Isaac. To the concubines' sons... he gave gifts. Then, while he was yet alive, he sent them to the country of the East, away from Isaac” (Gen. 25:5-6). Tanchuma stresses, “He removed them far from Isaac.”
Thus, there are two reasons for Abraham's banishing Ishmael and the other sons of the concubines: first, lest Isaac's sons should learn from their evil deeds; second, that these other sons who were born in the Land would forever think the Land was theirs and hate Isaac and his son Israel for taking it all for themselves. Sarah understood both reasons, hence she added, “The son of this slave will not share the inheritance” of the Land with Isaac, and since he would not inherit it, he would always hate Isaac and try to kill him. She, therefore, demanded that he be banished from the Land.
Ishmael's hatred for Israel is from ancient times and stems from Israel being Abraham's seed. Ishmael is jealous of Isaac's seed, who were chosen to be G-d's people, while he, Ishmael, was invalidated. Tanchuma (Vayelech, 2) teaches: “My beloved had a vineyard in a very fruitful hill, [and he dug it and cleared away his stones]” (Isaiah 5:1-2). The “vineyard” refers to Israel. “He dug it” refers to Abraham, for G-d got rid of his refuse, such as Ishmael. “He cleared away its stones” refers to Isaac, from whom emerged Esau. And the Mishna teaches (Nedarim 31a), “If someone vows not to derive any benefit from 'the offspring of Abraham,' he is forbidden to derive benefit from any Jew, but permitted to derive benefit from a non-Jew.” The Talmud then comments: What about Ishmael? It says, “It is through Isaac that you will be credited with offspring” (Gen. 21:12). And what about Esau? It says, “through Isaac” - but not all of Isaac. Thus, Ishmael was removed from the category of Abraham's offspring, and he has no portion in Abraham, his offspring or his land. This they will never forget, and they have harbored this resentment all along.
Already in the days of Alexander of Macadon, there was an incident described in Sanhedrin 91a: “...Another time, the descendants of Ishmael and Ketura came with Israel for litigation before Alexander of Macedonia. They said to Israel, Eretz Israel is yours and ours, as it says, 'these are the chronicles of Ishmael, son of Abraham' (Gen. 25:12), and, 'these are the chronicles of Isaac, son of Abraham' (Ibid., v. 19). ...Gevia ben Pesisa asked them, 'from whence are you bringing proof?' They responded, 'from the Torah'. He then said, 'I, too, will bring proof only from the Torah, for it says, 'Abraham gave all that he owned to Isaac. To the concubines' sons...he gave gifts, [and he sent them off]'(Gen. 25:5-6). If a father gives his sons an inheritance during his lifetime, and he sends them away from one another, can any of them have claims against any other?” Here we see that over a thousand years after Ishmael's death the Ishmaelites were still claiming the land. They ignore all the arguments we put forth, just as they ignore what the Talmud states (Sanhedrin 59b) regarding circumcision: “It is Abraham whom the Torah originally admonishes 'You must keep My covenant – you and your offspring throughout their generations' (Gen. 17:9)... What about obligating the Ishmaelites [in circumcision, since they are Abraham's seed]? It says, 'it is through Isaac that you will gain posterity' (Gen. 21:12). Thus, the Torah states explicitly that only Isaac, and not Ishmael, will be called Abraham's seed. Yet, what do the Ishmaelites or any other nation with a claim to the Land care what we say? Since they are our blood enemies and will never accept the authority of Israel and G-d, they have no place in the Land... Besides all this, we know that in the footsteps of the Messianic era, Ishmael will rise up against Israel and try to annihilate them.
R. Yitzchak said: The Torah need only have begun from Ex. 12:2, “This month shall be unto you the first of the months,” [introducing the first commandment given to Israel]. Why then did it start with the Genesis narrative?... It was so that if the nations of the world ever say to Israel, “You are thieves,” they will respond [that “the entire world is G-d's property. He created it and gave it to whoever is fitting in His eyes (Jer. 27:5); according to His will He gave it to them and according to His will he took it from them and gave it to us”] (Rashi Gen. 1:1). Likewise, the Midrash says (Bereshit Rabbah, 1:2), “It was so that the nations would not castigate Israel and call them “a nation of plunderers”. R. Yitzchak did not say there, “because of the seven nations” but rather, “the nations of the world”, to inform us that all of the nations will join those nations who once inhabited the Land, be they the seven nations or Ishmaelites, with the claim that Israel are thieves and plunderers, and on that day, Israel shall stand alone. It follows that those same laws that applied to the seven nations [that is, to remove them from the Land] apply to all the nations that live in Eretz Yisrael in every age. This includes those of our age, who view Eretz Yisrael as their own land and soil, and who view the Jewish People as a nation of conquerers, robbers and thieves.
After all, what difference is there as far as G-d's warning that “those who remain shall be barbs in your eyes and thorns in your sides, causing you troubles in the land” (Num. 33:55), between the seven nations and between any nations that dwells in the Land, views it as its own, and then Israel come and conquer it from them? Surely it will feel that same hatred and that same fierce will for revenge as did the seven nations. This logic appears already in Or HaChaim (Num. 33:52): “You must drive out”: Although the verse said of the seven nations, “You shall not allow any people to remain alive” (Deut. 20:16), here, the Torah is talking about other nations found there besides the seven. It therefore was careful to say, “all the Land's inhabitants”, meaning, even those not of the seven. They, too, will always harbor resentment against Israel and will never resign themselves to us, but will await the “right” moment to rebel. As for their ostensibly having submitted nowadays, that is only out of fear and the inability to claim victory for the time being.
Abraham, out of his mercy and kindness, did not wish to see the evil done by Ishmael, especially with him being his son. G-d therefore had to command him, “Let it not be grievous in your sight because of the lad” (Gen. 21:12). Mercy towards the cruel is not a good trait. Quite the opposite, one is duty-bound to separate oneself from the evildoer even if this is a difficult step, and even if it appears cruel. There can be no coexistence between evil and upright people – only separation. [Likewise,] the death of the wicked is infinitely preferable to the death of the righteous, and eradicating evil is infinitely superior to eradicating good.
Compiled by Tzipora Liron-Pinner from "The Jewish Idea" of Rav Meir Kahane, HY"D