פירוש על בראשית 21:11

על אדות בנו ON ACCOUNT OF HIS SON — because he heard that he had taken to degenerate ways (Exodus Rabbah 1:1). The real meaning, however, is because she (Sarah) had told him to send him away.

AND THE THING WAS VERY GRIEVOUS IN ABRAHAM’s SIGHT ON ACCOUNT OF HIS SON. That is, for he had taken to degenerate ways. The plain meaning, however, is that he was grieved because she had told him to send him away. Thus the language of Rashi.
The correct interpretation appears to me to be that Scripture is speaking in honor of Abraham, saying that the reason why the matter was very displeasing to him was not due to a craving for his concubine and his desire for her. Therefore, if she had told him to cast out only the maidservant, he would have done her will. But it was on account of his son that he was very much incensed and did not want to listen to her. But the Holy One, blessed be He, told him that he should not resent it at all, neither for the son nor for the maidservant, and that he should listen to Sarah’s bidding for it is through Isaac alone that his name will be carried on, while Ishmael will not be referred to as his offspring. Now because Abraham feared lest an accident happen to Ishmael upon his sending him away, He told him that He will make a nation of him and He will bless him since he is indeed his son.

על אודות בנו. On account of his son. Abraham was afraid that the expulsion would result in Ishmael pursuing unwholesome activities because he felt rejected. He had to be concerned about this since Ishmael was his son after all.

וירע הדבר...על אודות בנו, even though Ishmael was the son of a slave-woman, he was at the same time also Avraham’s son, and he loved him as a father loves one’s son, especially seeing that he was his firstborn. He was merciful towards him like a father is merciful to all his children. Moreover, he had taught him to behave and had taught him the ways of the Lord. In fact, if he, Avraham, had taught all and sundry the ways of the Lord, he had most certainly not neglected to teach these ways to his own son. Therefore, the request by Sarah to expel his own son was a source of great chagrin to him. Avraham kept his chagrin to himself and did not express anger at his wife as he was concerned with preserving שלום בית, peaceful marital relations with his wife. This was the state of affairs until G’d intervened in the matter.

On account of his son: As Sarah had said (Genesis 21:10), "and her son" - implying that she wanted Avraham to act towards Yishmael like towards the son of a maidservant, since her offspring is like (has the same status as) her and does not go after the father. But he knew it was not so. As behold, he had freed her and taken her as a wife. And it is like it is written above (Genesis 16:15), "and [Avram] called the name of his son."

על אודות בנו. “on account of his son.” According to Rashi, Avraham feared that expelling him would lead to his abandoning the teachings he had learned in his home. Nachmanides writes that the Torah praises Avraham in this verse for not objecting to the demand for the expulsion of his concubine and her son as he was so fond of Hagar, but that he was troubled that the expulsion of his son would even further inhibit his growing up in the monotheistic Abrahamitic tradition. He waited until he had been instructed by G’d to follow Sarah’s instincts when it came to pedagogy. Seeing that Avraham was concerned about the personal security of Ishmael, He promised him that his son Ishmael would develop into a great nation. On the other hand, Yitzchok would be the recipient of G’d’s comprehensive blessings.

And it was bad: Sarah began that he should drive out the maidservant, since she thought that the main love of Avraham was for his concubine, and he loved his son along with her, as well. But Scripture testifies that the essence of what was bad in the eyes of Avraham was "on account of his son."

For he heard that he fell into bad ways. Rashi brings both the Midrashic and the simple explanation because with the simple explanation alone, a question arises: In v. 12, Hashem tells Avraham, “Do not consider this wrong on account of the boy and your slave-woman.” This implies that Avraham was perturbed also about his slave-woman. So why does our verse mention only “his son”? Thus Rashi explains our verse [Midrashically,] that Yishmael fell into bad ways—something not relevant to Avraham’s slave-woman. But without the simple explanation, another question arises: [Since Avraham was not perturbed about sending Yishmael away,] why does Hashem then say to Avraham in v. 12: “Do not consider this wrong... regarding all that Sarah tells you, listen to her...”? What does listening to Sarah have to do with Yishmael’s fall into bad ways? Furthermore, the reason that Scripture then gives, “For only through Yitzchok will seed be considered yours,” is irrelevant to Avraham’s concern over Yishmael’s falling into bad ways. This is why Rashi needed the simple explanation as well. It seems that [Rashi learned] the two explanations from על אודות בנו, for it appears to be repetitious. Since אודות means the same as על, why say על twice? It could have simply said על בנו, as in the next verse: אל ירע ... על הנער. Perforce, it comes to tell us that Avraham was perturbed about two things. But only for sending them away did Hashem say (v. 12), “Do not consider this wrong...” (R. Meir Stern)

Diese ganze Sache erschien dem Abraham außerordentlich bös, hart, רע, (rad. רעע) es war ein Bruch in seinen Vorsätzen, in dem Bilde, das er sich von seiner Zukunft entworfen hatte, und zwar nicht bloß in Beziehung zu Ismael, denn Gott sagt nachher zu ihm: על הנער ועל אמתך, sondern auch in Beziehung auf dessen Mutter. Beides erschien ihm nicht gut, jedoch nicht etwa aus einer persönlichen Neigung für Hagar, sondern על אודות בנו lediglich aus Rücksichten für seinen Sohn, wörtlich: über Veranlassungen seines Sohnes, über Beweggründe von seinem Sohne (אודו Plural von אוד, die Handhabe, der Hebel). Abraham war sicher nicht entgangen, was Sara bemerkt. Allein Abraham dürfte gedacht haben: wenn Ismael schon in seinem Hause von dem Ernst eingebüßt und מצחק geworden, und wenn ferner Hagars Einfluss, obgleich gewiss von Abraham teilweise paralysiert, schon jetzt auf Ismael so groß gewesen, wie wird dies erst dann sein, wenn beide aus dem Abrahamshause fern und Ismael ganz Hagars Einfluss hingegeben sein wird!

And this thing was very bad: Meaning to say, it was difficult in his eyes about Hagar, but it was very difficult for him about his son. Therefore He said to him (Genesis 21:12), "Do not let it be bad in your eyes concerning the youth and concerning your maidservant."

Another meaning of this expression is that Abraham resented Sarah's describing Ishmael as merely "the son of this slave-woman." G'd now interfered by telling him that Sarah was entirely justified. When G'd pointedly referred to Ishmael as הנער, the lad, and not as "your son," He made it plain that only Isaac would be considered an extension of Abraham. G'd added: "also the son of this slave-woman," when He referred to Ishmael as having a major role in history. When the Torah describes Abraham as complying with Sarah's i.e. G'd's request, he no longer refers to Ishmael as "his son," but only as "the child."