The Torah portion Tazria opens by saying:1 “When a woman conceives and gives birth to a boy…. On the eighth day, [the child]… shall be circumcised.” This is so only if the infant is healthy; if the child is not completely well, milah (the ritual of circumcision) is delayed until he is fully recovered.

The Rambam explains why only a healthy child is circumcised:2 “A threat to life sets everything else aside; it is possible to circumcise later on, but it is impossible to return a Jewish soul [to its body after its passing].”

The Rambam’s exposition — “it is possible…” — indicates that he is providing two reasons:

“The threat to life sets everything else aside” means that even if the mitzvah of circumcision can never be performed because of “a threat to life,” it is to be forever forfeited, since “a threat to life sets everything else aside.”

The second reason — “it is possible to circumcise later on” — suggests that when milah is delayed because of ill-health, nothing is really lost. We thus understand that performing the mitzvah of milah at a later date affects the previous days as well, so much so that, retrospectively, it is equal to circumcision on the eighth day.

How can an action so affect the past?

We must also understand the following: At the conclusion of the second reason of “it is possible to circumcise later on” the Rambam adds: “but it is impossible to ever return a Jewish soul.” Seemingly, these words are more closely related to the first reason of “A threat to life sets everything else aside”?

Chassidus explains3 that milah allows the drawing down of a Divine illumination far greater than man’s service alone could accomplish; the illumination reflects an “arousal from Above.” So long as a person is uncircumcised, his state acts as a barrier to this light. Milah removes this barrier.

The same is true regarding the “entry of the holy soul” accomplished through circumcision:4 The ritual draws down a level of soul that transcends intellect.5 This, too, cannot be realized through man’s service alone — it forms an essential part of every male Jew, and is merely revealed through milah.

Since circumcision merely exposes a pre-existing spiritual state, it is able to affect the past as well. If milah is never performed, then the spiritual state remains concealed. But once milah is performed and the pre-existing state is revealed, it influences the past as well.

Accordingly, the Rambam states: “but it is impossible to ever return a Jewish soul” after both reasons, in order to explain how milah performed “later on” is considered as if it were done on time.

A Jew’s connection with G‑d transcends all bounds, and is always whole. “It is impossible to ever return a Jewish soul” thus means that the bond with G‑d can never be “returned,” i.e., severed.

This being so, all that is required is for this bond to be revealed. This is accomplished by milah even “later on” — even then, its effect is the same as that of milah performed in its proper time.

Based on Likkutei Sichos Vol. III pp. 979-983.