the dual mitzvos of milah

The Netziv in Harchev Davar at the end of the parsha quotes a machlokes between Rashi and the Rambam as to what being "meifer briso shel Avarahm Avinu" (Avos ch 3) means.  According to Rashi, being "meifer bris" means not doing milah.  According to the Rambam, it means being "mosheich b'orlaso," trying to cover up the milah.  Rambam writes at the end of hil milah: וכל המפר בריתו של אברהם אבינו והניח ערלתו או משכה אע"פ שיש בו תורה ומעשים טובים אין לו חלק לעולם הבא:

Netziv uses the shitas haRambam to explain the language of the pesukim (17:13).  Once you do the act of milah, "hi'mol yimol y'lid beischa...," isn't it obvious that "v'haysa brisi b'bisarchem" will follow?  Why does the Torah add these words?  Netziv answers that these words are a separate mitzvah to maintain the state of being mahul and not be moshech b'orlaso.

The fact that there are to commandments here, not one, also helps us understand why there are two brachos at the time of a bris, one on the milah, and one l'hachniso b'briso shel Avraham.  One bracha is on the act of milah itself, and one bracha is on the mitzvah of "v'haysa brisi b'bisarchem," maintaining the state of being mahul.

I would add as well that this chiddush helps explain the gemara (Menachos 43) that tells us that when David haMelech entered the bathhouse he became sad since he was bereft of mitzvos until he remembered that he was mahul and had that mitzvah.  The mitzvah of milah was done to David I assume when he was eight days old -- it is not a mitzvah that he is doing right then in the bathhouse?  (See Mahara"Ch Ohr Zarua quoted here.)  Perhaps according to Netziv it was not the mitzvah of "himol" that David was thinking of, but rather the mitzvah of "v'haysa brisi." (see this post of R' Eliezer Eisenberg's as well.)

Netziv adds another layer to his argument (this part is very tersely put, so please see inside in case I got it wrong) that there is a second mitzvah that requires its own bracha by referring you to the Rosh on birchas eirusin that we discussed earlier this week.  Rosh holds that since it is possible to fulfill pirya v'rivya without getting getting married, e.g. you can take a pilegesh, therefore, eirusin does not warrant a birchas hamitzvah.  Rosh asks on himself: so why do we say any bracha on shechita -- you can become a vegetarian and eat without killing animals?  The Rosh gives three answers: 1) you can have children without getting married, but you can't have kosher meat without doing shechita; 2) the Torah expresses shechita as a command, "v'zavachta ka'asher tzivisicha," as opposed to kiddushin which us expressed conditionally, "ki yikach ish isha;" 3) the mitzvah of offering korbanos requires shechita, so once there was a takana for a bracha on shechting korbanos Chazal expanded it to include any act of shechita.  

The second answer of the Rosh is a tremendous chiddush: even though in lomdus eirusin and shechita are the same, since the expression the Torah uses to formulate the mitzvah in one case is a command and in the other case a condition, it makes a difference with respect to the nature of the bracha.  So too here, since "v'haysa brisi" is expressed as a mitzvas aseh, not a lav, even though it is essentially avoiding doing something, it therefore warrants a bracha.  (The Netziv then goes on to prove that you can recite a bracha on an issur aseh.)

Earlier in the week I wrote that Rambam who holds birchas eirusin is a birchas ha'mitzvah is l'shitaso that kiddushin is a mitzvah in its own right, while Rosh disagrees and holds that it is not.  R' Nissan Kaplan makes a beautiful diyuk in the Rosh that this is not the case.  If the Rosh held that eirusin is not a mitzvah, then he would have no question on why there is a bracha on shechita but not eirusin -- one is a mitzvah, one is not!  Al korchacha the Rosh also holds that eirusin is a maaseh mitzvah, but since it can be avoided, it does not warrant a bracha.  The comparison to shechita is now much sharper -- there too, there is a mitzvah, but it is a mitzvah that can be avoided if one goes vegetarian, so why does it get its own bracha?