Mitzvat Aseh 7 - To Swear in Hashem's Name

The Mitzvah

We are commanded to swear in Hashem's name when it is necessary to support or refute something of significance. By doing so, we come to increase Hashems greatness along with honor and majesty. The source for this Mitzvah is: "U'Vishmo Tishvae'ah, in His Name you shall swear" (Devarim 6:13).

Yet there seems to be a contradiction here since the Torah also says "don't swear". This, Rambam says, is referring to a swear or vow that does not need to be made. In fact, doing such a thing is a negative commandment, and, therefore, a sin. Nevertheless, when the situation demands a swear, a mitzvah is fulfilled.

As such, it is forbidden to swear on any object or entity that is not Hashem, for example the sun, or Moshe Rabbeinu, even though it may be very clear the person making the swear means to say or implies "the Master" of the sun or Moshe (i.e. Heshem). So too, one is unable to join separate objects in a swear with Hashem, for we learn (Talmud Bavli, Tractate Sukkah 45a) that anyone who joins in a swear with Hashem will be uprooted from this world.

Lastly, this Mitzvah comes to explain what we learn in Tractate Temurah 3a: How do we know that one who swears fulfills (will fulfill) the mitzvah? For the Torah says: "U'Vishmo Tishvae'ah, in His Name you shall swear".

The Commentary

Ramban makes three points which I was able to understand:

1. The Mitzvah to swear in His Name stems from the same basic idea we've seen before. That is, to do what we can to serve and love Hashem. If a swear will keep us honest to perform accordingly, one may be made.
2. This Mitzvah, like the one before it (Dveikut, clinging) is repeated once more in the Torah. This raises a problem because in point #1, Ramban downgraded Mitzvah #7 to a Reshut, one step below obligatory, and no Mitzvot Reshuyot (non-obligatory Mitzvot) are repeated. Therefore, Ramban says, the second iteration of this Mitzvah falls under the category of prohibitions against Avodah Zarah (Idol/Foreign Deity worship). Rambam himself supports this idea when requiring that one may not include other objects along with the swear.
3. The Midrash Rabi Tanchuma pretty much precludes this Mitzvah from ever being performed. The midrash says that the only way we would be able to make a swear in Hashem's name is if one met all of the criteria outlined in the context of the pasuk it is mentioned in, namely to fear Him and serve him (and later on, to cling to Him). But as we learned before, "Hashem is a consuming fire", preventing us from meeting all of the conditions. Now, even if we follow what we learned about clinging to Talmidei Chachamim instead, and make those items the criteria, it is still impossible for us to determine who is and is not a Talmid Chacham in Hashem's eyes. Ramban continues even further excluding the possibility of of fulfilling this mitzvah saying that the Mitzvah may have been repeated to warn us not to do it, even when all of the conditions are met.

It is for these reasons that Ramban does not include this Mitzvah in his count.