At the height of joy in Abraham's household, during the great feast celebrating Isaac's weaning, a deep fracture suddenly appears. Sarah observes Ishmael's behavior, prompting a dramatic decision to expel Hagar and her son. This singular moment is fraught with underlying tensions of jealousy, fierce struggles over inheritance, and the looming fear of moral corruption.
The simplest understanding of Ishmael’s behavior is that he was merely engaging in the natural, innocent play of a teenager, and Sarah’s reaction stemmed from a mother’s protective jealousy over her smaller, younger son [אבן עזרא, חזקוני, יהל אור]. Contrast this with a much broader perspective that views his actions as deeply cynical. He may have been mocking the extravagant feast out of resentment, bitter that his own weaning was never celebrated so grandly [רמב״ן, רלב״ג, תולדות יצחק]. Others suggest the mockery was directed at the very concept of Isaac's birth to elderly parents [רד״ק], or that Ishmael dismissed the miracle entirely, claiming Abraham only threw the feast to appease his beloved wife [העמק דבר]. More severely, Ishmael may have been echoing the cynics of the time, spreading rumors that Sarah had actually conceived through Abimelech [ספורנו, מלבי״ם, הכתב והקבלה, ביאור יש״ר]. Ultimately, Ishmael had absorbed Abraham's ideals just enough to view them with irony, proving himself entirely unfit to carry on the family legacy [רש״ר הירש].
Beyond mere cynicism, the behavior pointed to a fierce struggle for succession. Ishmael's laughter may have masked a dark anticipation of Abraham and Sarah's passing, as he expected to inherit the entire estate [שד״ל, צרור המור]. He openly defied Isaac's status, demanding the double inheritance portion traditionally reserved for the firstborn [רש״י, רשב״ם, תורה תמימה]. The most severe interpretation identifies his actions as hinting at the three cardinal sins: idolatry, illicit relations, and bloodshed. According to this view, Ishmael engaged in indecent acts, worshipped idols, and even shot arrows at Isaac with murderous intent, disguising the assassination attempt as a harmless game [רש״י, גור אריה, שטיינזלץ, אם למקרא]. While some question how such heinous crimes could occur in the home of a righteous man like Abraham—preferring to view the conflict strictly as an inheritance dispute [רמב״ן]—others explain that these grave sins are characterized as playful mockery because they are deceptive acts that distort the proper order of the world. Recognizing this profound moral threat, Sarah acted swiftly to remove the influence before Isaac could be corrupted [גור אריה].
Sarah deliberately identifies Ishmael not by his name, but by his maternal lineage, viewing his corrupt behavior as a direct product of his roots. Recognizing that children often echo their parents, she concluded that Hagar had actively incited him to mock Isaac [מלבי״ם, הכתב והקבלה, ספורנו]. This identification also highlights Ishmael's gravitation toward the Egyptian culture of his mother—a society steeped in idolatry and immorality—rather than the path of Abraham [שפתי כהן, משכיל לדוד, צרור המור]. In general, the shifting titles used for Ishmael throughout the narrative consistently reflect the speaker's underlying attitude toward him [ברכת אשר על התורה]. By emphasizing his status as the son of a maidservant, Sarah pointed to a severe breach of social order; a servant mocking his master warranted harsh punishment. Yet, she settled for banishment, aiming primarily to sever any inheritance rights he might claim alongside her son [רמב״ן]. Expelling Hagar alongside Ishmael also prevented the illusion that Hagar was a full-fledged wife, a status that would have only strengthened Ishmael's future claims to the estate [אברבנאל].
Even the acknowledgment of Ishmael as the son born to Abraham is understood as an extension of the mockery itself. Ishmael arrogantly boasted that he was the only son whose paternity was indisputably tied to Abraham, casting further doubt on Isaac's true lineage [הכתב והקבלה]. Conversely, this reality highlights a tragic distinction: while Ishmael was physically born to Abraham, his internal nature, character, and actions remained entirely those of the Egyptian woman's son [שפתי כהן].