בראשית, פרק כ״א, פסוק ד׳

The entry of Isaac into the covenant marks a profound historical milestone. He is the first child to undergo circumcision exactly on the eighth day after birth [ביאור שטיינזלץ]. Fulfilling this duty on its precise date reflects immense dedication. Because Isaac was born to elderly parents, one might naturally assume the infant would be frail. Under such circumstances, a father might reasonably consider delaying the procedure until the child grew stronger and more robust. Yet, Abraham did not wait, performing the act immediately on its designated day [תולדות יצחק].

Performing this act on an eight-day-old infant carries a unique sense of joy. An adult required to undergo such a painful procedure must consciously consent, a process that can easily lead to hesitation or resistance. In contrast, an infant grows up already sealed within the covenant. This is compared to a person who discovers a great treasure and becomes wealthy without any effort. The child secures the merit of the commandment by the time he reaches an age of understanding, completely spared the internal struggle of making the decision [פרדס יוסף].

Abraham carried out God's directive with absolute precision and completeness. He was well-versed in the oral laws and strictly adhered to their details, ensuring the procedure took place during the day rather than at the onset of the eighth night [העמק דבר]. Furthermore, he acted with great eagerness, performing the procedure at the break of dawn. This contrasts with Abraham's own circumcision, which occurred in the middle of the day as part of his personal conversion process [צפנת פענח].

Acting directly from a divine command highlights Abraham's spiritual greatness. A person who fulfills a duty because God commanded Him to do so earns a greater reward and achieves a more complete spiritual acquisition than someone who volunteers without an obligation [תיבת גמא]. Because this instruction comes directly from God, it serves as an eternal directive for all future generations, firmly establishing a father's obligation to circumcise his son [תורה תמימה].

The primary approach among commentators is that the responsibility for this act rests exclusively on the father, completely exempting the mother [רד״ק, תורה תמימה]. Although women are generally exempt from positive commandments bound by time—and this procedure must typically be done during the day—this specific exemption is still necessary. It ensures the mother remains exempt even according to legal opinions suggesting that a delayed procedure may validly be performed at night [תורה תמימה].