The gemara (Brachos 8) tells us that a person must be “mashlim parshiyosav im hatzibur,” complete the study of parsha with the community by reading each parsha two times and its targum once, shenayim mika v’echad targum. “With the community” is usually understood to mean that a person should time his study of the parsha so that it coincides with what the community will read on shabbos. Some Rishonim understand shenayim mikra as a preparation in case one is called up for an aliya and has to read the parsha. (If one falls behind in shenayim mikra whether one should skip a parsha to catch up or go in order may depend on whether this or some other reason is the motivation for the din.) The Sefer haPardes, however, understands the gemara to mean that shenayim mikra is a communal activity -- before the Torah was read the tzibur would join together in studying the parsha with its targum. (Parenthetically, I think this may be a nice idea to implement on a scaled down level in some shuls. Too often the reading of the Torah is viewed as some kind of ritual performance or a part of tefilah instead of an opportunity for real study. Imagine a 5 minute guided chavrusa session as an introduction to the parsha – why not?)
The gemara adds that this obligation of shenayim mikra v’echad targum includes even “Ataros v’Divon,” referring to the names of two of the cities requested by Reuvain and Gad in our parsha (BaMidbar 32:3). Rashi writes that even though these are just place names and the targum adds no interpretation, there is still an obligation to read the targum along with the text.
Tosfos asks: If Rashi is correct, why does the gemara select specifically this pasuk to make its point? The gemara could just have easily have said to read the targum to “Reuvain, Shimon…” Secondly, the targum does in fact interpret the names “Ataros v’Divon”!
(There is a girsa change in the margin of the gemara that changes the text to read “Divon v’esAtaros.” This pasuk appears later in the parsha (32:34) and there the targum does not interpret the names, avoiding Tos second question.)
Tosfos therefore suggests that the gemara singled out “Ataros v’Divon” because there is a targum on this pasuk, albeit the lesser known targum yerushalmi and not onkelus. The gemara’s chiddush is that reading the targum yerushalmi is still preferable to not reading any targum at all.
It is not clear whether Tos’ disagrees with Rashi only with regards to pshat in the gemara or whether Tos disagrees with Rashi's halachic conclusion. In other words, would Tosfos also require a third reading of a pasuk even where the targum just recapitulates the text, e.g. in the case of “Reuvain, Shimon…? It’s also not clear whether Tos acceptance of interpretations other than onkelus extends only the other targumim like the targum yerushalmi, or would other translations and interpretations pass muster as well, e.g. Artscroll?
The Torah Teminah offers another novel reading of this gemara. According to the T”T the chiddush of the gemara has nothing to do with targum, but has to do with the requirement of shenayim mikra, reading the text itself. In the context of Reuvain and Gad’s request for land, the list of cities named really does not seem to add anything. The parsha is just as understandable, just as readable, if that entire pasuk were omitted. The gemara’s chiddush is that even in this case where an entire pasuk seems extraneous, one is still required to read it to fulfill the obligation of reviewing the parsha.
This sounds like a remarkable chiddush. Is this the only pasuk that seems like it serves no function? It stands out more than the lists of genealogies in Sefer Braishis, just to take one example? Secondly, just because the pasuk appears extraneous does not mean it is so. It did not take more than a glance at a Mikra’os Gedolos to find meforshim who discuss why particular cities were named (e.g. Seforno, Ohr haChaim). [Update: see the Rabeinu Bachye who specifically makes the point that these pesukim are important despite appearances to the contrary; he explains their meaning al pi sod.) The T"T is certainly an interesting twist, but I'm not convinced it's better than Rashi or Tos' approach.