Parshat Chayei Sarah leaves us with a very strong question regarding how parents should deal with problem children. Avraham took the merciful approach. Already in לך לך, upon being informed that Sarah would have a child, Avraham's responds, לו ישמעאל יחיה לפניך )בראשית יז:יח(. Hashem has to reassure him that, although Yitzchak will be His "chosen one," He has not forgotten Yishmael. Later, in Vayera, Avraham is extremely hesitant about sending away Yishmael, despite Yishmael's negative influence over Yitzchak, who was then a young child. Hashem had to intervene and tell Avraham to send away Yishmael (בראשית כא:יב). Once again, Hashem must reassure Avraham that He will also care for Yishmael. Finally, in this week's parsha, Avraham is confronted with another such situation. Following Sarah's death, Avraham has six children (ועי' ספורנו לבראשית כה:ב) with his new wife, Keturah. Avraham decides, as his last recorded action, to send away all of these sons, so that Yitzchak will remain as his lone heir. Although we know that Yishmael was not the finest individual (and we can assume that the same was true of Avraham's other sons), it seems a bit harsh to send them away. Avraham certainly cannot be blamed for sending away Yishmael, because Hashem forced him to do so. However, sending away Keturah's sons is a bit more difficult to accept. Avraham acted without any Divine command. While one could argue that Avraham was simply continuing the same process of sheltering Yitzchak which Hashem started by commanding him to send away Yishmael, the situations are not parallel. Yishmael was a teenager with a baby brother whom he could easily influence. Assuming that the Torah is written in chronological order (which fits in well here, because it means that Avraham remarried immediately after Yitzchak was comforted from Sarah's death), Yitzchak was a married forty year old by the time the oldest son of Keturah could have been born. How could these of babies negatively influence the grown up Yitzchak? In what way was Yitzchak's development as the "chosen one" endangered by the presence of Keturah's sons?
The Torah passes no explicit judgment on Avraham's decision. One could go away from this week's parsha under the impression that Avraham made a mistake. However, this is unlikely, considering that immediately after Avraham's death Hashem blesses Yitzchak (בראשית כה:יא), fulfilling what were surely Avraham's wishes when he sent Keturah's sons away. As if to stress his status as the only son of Avraham living in Israel, Yitzchak settles in באר לחי ראי, which was originally named by Hagar to commemorate the angel's promise of Yishmael's birth (בראשית טז:יג). Hashem seems in no way displeased with Avraham or Yitzchak (who could have also been held accountable, considering that he was in his forties by this time) for evicting Keturah's sons. We are still left with the question: If Yitzchak was no longer young and impressionable, why did Avraham evict Keturah's sons?
I would like to suggest that Avraham was not concerned with them having a negative religious impact on Yitzchak. Rather, he was concerned with the political problems that could be caused by leaving other sons of Avraham in Eretz Canaan. In order to prevent the other nations from claiming, "We are the sons of Avraham; Eretz Canaan is ours, too," Avraham wanted them as far away as possible. This would explain why Yitzchak's first action after his father's death was to move to באר לחי ראי. He went straight to the place where the angel had predicted Yishmael's birth, showing that he alone had inherited Avraham's rights to Eretz Yisrael. One may ask, though, what gave Avraham the right to evict his other sons for political reasons? Why could Avraham not leave them there and let Yitzchak children deal with their own political problems when they arise?
The answer to this may be found in the haftarah. Here, Bnei Yisrael are faced with the problem of picking a successor for David. David knows that Shlomo is the right choice, but it is apparent that few others are aware of this. Yoav, the army's Commander in Chief, and Evyatar, the Kohen Gadol both support Adoniyahu in his bid for the kingship. David initially does nothing, leaving his sons to sort out their own political problems. After being prodded to act by both Batsheva, Shlomo's mother, and Natan HaNavi, David finally appoints Shlomo as the next King. By this time, Adoniyahu has so much popular support that Shlomo must be anointed by the Kohen Tzadok (a practice which was never done for a son succeeding his father, unless there was a serious doubt as to whether or not this son would succeed his father). Since David had not yet endorsed Shlomo when Adoniyahu started campaigning, Shlomo is unable to penalize Adoniyahu for treason. The Navi is clear that David made a big mistake by not making it clear at a much earlier point that Shlomo would succeed him. The reason the Navi gives for the entire controversy is ולא עצבו אביו מימיו לאמר מדוע ככה עשית, "[Adoniyahu]'s father had never in his life criticized him by saying, 'Why did you do this?'" Later in Sefer Melachim, Shlomo pays the price for his father's hesitation, and is unable to firmly establish his hold on the throne until he executes Adoniyahu. Surely, it would have been better for David to deal harshly with Adoniyahu before a controversy erupted which ended with Adoniyahu's death.
From this story, we can justify Avraham's eviction of Keturah's sons relatively easily. Avraham had been previously told by Hashem that his children would someday be exiled, and some day they would return and conquer Eretz Canaan from the Emorim. Hashem was clear that Bnei Yisrael would have every right to destroy the Emorim, because they deserved it for their own sins. However, Avraham wanted to prevent Bnei Yisrael from getting caught up in a battle with his other descendants over Eretz Canaan. He realized that a conflict like that would only end with one side (whom Hashem stated would be Bnei Yisrael) killing or expelling the other side. Avraham was looking to prevent his type of conflict from arising, in order to prevent his other sons from being forced to die or be exiled in a later time.