At the beginning of the Parsha, the Torah states that if a woman gives birth to a male child, then that child must be circumcised on the eighth day of his life (ויקרא י"ב:ג').  Earlier in the Torah, at the end of Parshas Lech Lecha, the Torah states that Bris Milah is a sign of an agreement between Bnai Yisrael and Hashem, and that any male child who has not fulfilled this obligation will be punished with Kareis )כרת(, and be cut off from the Jewish people (בראשית י"ז:ג').  The possible manifestations of Kareis in general are discussed by Chazal; the Gemara in Moed Katan )דף כ"ח.( mentions two understandings.  One is that Kareis is characterized by death at the age of fifty, and one is that it is characterized by death between the ages of fifty and sixty.  Some say that Kareis is also manifested by the person remaining barren throughout his lifetime.  It should be noted that the Rambam )פרק ח' מהל' תשובה הלכה א'( holds that Kareis is also a spiritual cutting off of the person from Olam HaBo.

                With regards to Bris Milah, the Rambam states )פרק א' מהל' מילה הלכה א'-ב'( that the obligation to assure that the Milah gets done is upon the father, or in the case of slaves, upon the master.  If these two parties mentioned do not fulfill their obligation, they have not performed a positive Mitzvah of the Torah, but they do not receive Kareis.  That punishment is only for the one who himself is supposed to be circumcised.  If the father or master renege on their responsibility, it is then up to the Beis Din to carry out the Mitzvah in its proper time.  However, one should not circumcise someone else's son without the father's knowledge unless the father refuses to have his son undergo the procedure.  A child who remains uncircumcised as a child is obligated, upon reaching the age of Bar Mitzvah, to personally make sure that the Mitzvah is completed.  Every day that he neglects the Mitzvah, he has indeed negated the positive Mitzvah, but he is not punishable with Kareis until he dies having remained intentionally uncircumcised.

               The Rambam, in his Peirush HaMishnayos in Shabbos )פרק י"ט משנה ו'(, states that the non-fulfillment of Bris Milah is on a different level than the non-fulfillment of other positive Mitzvos, since each and every day during which one remains uncircumcised constitutes a new negation of the requirement of performing the Bris Milah at its proper time.  Once the Bris is completed, however, the transgression is erased and is replaced by a Mitzvah.  The Rambam also says )שם( that anyone who is aware of such a child in that situation and does not see to it that the Milah is performed is also responsible for the loss of the positive Mitzvah, as if it was his own son.  Once the child grows up and has assumed liability for his own actions, though, no other person is held responsible for this individual's negligence.  It is then he alone who is bidden to have himself circumcised immediately, and he alone has transgressed the positive Mitzvah until it is done.  Once the Milah is performed, even if it is at the end of his days, he has fulfilled a Mitzvah, and the transgression is erased.  If, however, he dies an ערל (uncircumcised), he is then punished with the appropriate form of Kareis.  This Mitzvah is totally unique, says the Rambam )שם(, since its violation is not punishable by Malkos, lashes, which are usually given to one who deserves Kareis, and he thus dies with his sin. 

               The Raavad, commenting on the aforementioned view of the Rambam in his Mishneh Torah )הל' מילה שם הלכה ב'(, takes issue with the Rambam's opinion regarding the ערל not receiving Kareis until he dies, and states that it is not possible to say that this person would be exempt מן השמים, in the eyes of the Heavenly court, and he thus remains in a daily state of איסור" כרת," in violation of a prohibition deserving of Kareis.  The Kessef Mishneh )שם( explains that the Kareis mentioned by both the Rambam and the Raavad is referring to the one where the person dies prematurely, as mentioned in the above cited Gemara in Moed Katan )שם(.  The Rambam  )שם( holds, however, that this ערל is not given Kareis since he has not yet transgressed the Mitzvah, because he can always rectify the matter by having himself circumcised at any time.  The transgression would occur only if he dies after intentionally remaining an ערל; he then would receive a spiritual form of Kareis.  The Raavad )שם(, though, holds that from the day an ערל becomes an adult according to the Halacha, and he is thus liable for his actions, he is immediately deserving of a premature death; he can circumvent this punishment only through the fulfillment of the Mitzvah.  This is what the Raavad )שם( meant by the statement that the ערל remains in a daily state of an "איסור כרת", as explained above.  He is thus potentially eligible continually for premature death until he is circumcised.  Even though he might avoid the punishment, he is still, on a daily basis, transgressing the will of Hashem.  In other words, the punishment due to him מן השמים always remains in effect since he did something that might result in his death.  Since he put himself in that position, allowing himself to transgress the will of Hashem daily, the Halacha is that he is liable, on a daily basis, to premature death.  The Rambam )שם(, however, holds that since the individual is passively sitting back not performing the Milah, but can potentially amend his negligence, he is not considered liable at present for premature death.

                The Minchas Chinuch )סוף מצוה ב'( states that there is a practical difference between the positions of the Rambam )שם( and the Raavad )שם( in regard to one who neglected Milah במזיד, on purpose, all of his life, and then at the very end, when he wished to rectify the matter, became a שוגג, a unintentional violator, because something beyond his control prevented him from performing the Mitzvah.  According to the Rambam, such an individual would not be deserving of Kareis because at the end, he was not an intentional ערל, while according to the Raavad he would be, as he was potentially all along, because he was deserving of the punishment from the time he became Bar Mitzvah; doing the Milah would simply have been a way of avoiding the punishment, but since he couldn't do it, for whatever reason, the eligibility for punishment still remains.  Commenting on a Gemara in Kiddushin )דף כ"ט.(, however, the Chazon Ish (אבן העזר-נשים סימן קמ"ח, למס' קידושין שם בד"ה מיחייב איהו) is of the opinion that even the Rambam would agree that a מזיד, one who intentionally ignored the Mitzvah and then was prevented from doing it by something beyond his control, would indeed be deserving of Kareis, because otherwise we would never have someone deserving of Kareis, since every dying person, just before his death, is unable to do the Mitzvah because of a situation beyond his control, namely, his impending death.  The Turei Evven, explaining a Gemara in Rosh HaShanah )דף ו.(, writes that the punishment of Kareis for an ערל depends on his own definitive decision.  Once someone decides that he will definitely not undergo a Bris Milah, he is deserving of Kareis immediately. 

               Rav Menachem Mendel Schneerson, the Lubavitcher Rebbe, writes )לקוטי שיחות( that it was the merit of Bris Milah, which is without imitation, that gave the Jewish people the power to leave Mitzrayim.  May our study of this Mitzvah give us the merit to have this coming Pesach together with Moshiach in Yerushalayim!