1) i) The Chiddushei HaRim in his Sefer HaZechus explains: Most years Parshas Naso is the parsha read after Shavuos, the Yom Tov when we accept the Torah anew. Medrash contains what we are דורש, darshen, from the Torah, and the Zohar HaKadosh is מאיר אור התורה – brings the Torah to light, like it says many times in the Zohar, תא חזי - come and see, the Zohar lights up the Torah. Therefore, just after Shavuos when we accept the Torah, Hashem gave an abundance of strength to darshen and understand the Torah in a new light, therefore, the Medrash and Zohar have more to say on Parshas Naso than on any other parsha.
ii) R’ Tzadok HaKohen in Pri Tzaddik (ois 7) explains: In Parshas Naso we have the mitzvah of Birchas Kohanim, and one of the jobs of the Kohanim is to be mashpia Torah to Klal Yisroel, like it says: יורו משפטיך ליעקב ותורתך לישראל. Consequently, the hashpoas [effects] of Torah She’bal Peh which is Medrash is longer on Parshas Naso more than any other parsha.
2) Rabbeinu Bechayeh writes that the reason we give the sotah to drink from an earthenware vessel (כל י חרס) and not from a glass vessel, is because we are hinting that if one commits zenus [acts promiscuously] they lose out in this world and in the next, and they don’t get up by techiyas hameisim. Just like earthenware vessels that are broken can’t be fixed, so too a sotah has no takonah [fixing], glass, however, can be fixed by re-blowing it, therefore, a sotah drinks from earthenware and not from glass.
3) The Tosefta (Sotah 1:5) teaches: The Kohanim would make lots, and the Kohen that was selected - even if he was the Kohen Gadol, would go out and stand by the side of the sotah. He would then grab hold of her clothes, if they tore, they tore, if they revealed her, they revealed her, up until her heart, then he would uncover her hair.” The Chasdei Dovid explains: “Deciding which Kohen should take care of the sotah didn’t require lots, and any Kohen that wanted to do it could do it. However, the Tosefta is teaching us that if there weren’t any Kohanim offering to do it, as they were worried people will think they just want to see the sotah in her defiled state, then they would make lots.”
Based on the Chasdei Dovid it comes out that the lots carried out by the sotah were different to all other cases. Normally, lots were carried out as everyone was desperate to do the avodah [service], and to help decide who should merit to do it, lots were needed. By the sotah, however, no one wanted to do it, therefore, lots were needed in order to ensure it would get done.
The meforshim (Minchas Bikkurim and Chazon Yechezkel) explain: Just like there were lots to help determine who should undress the sotah and uncover her hair, there were also lots to determine who should give the sotah the special water to drink.
4) In Sanhedrin (85a) we learn that a son isn’t allowed to be a shliach Beis Din [messenger of Beis Din] to hit or curse his father or mother. We also learn in Sanhedrin (84b) that a son isn’t allowed to blood let from his parents. If the son gives his mother sotah water to drink and she is guilty and dies as a result, this is much worse than hitting or cursing a parent and it should be forbidden. On the other hand, the mother may be innocent and if she drinks the water she will merit lots of berachah (ונקתה ונזרעה זר ע ), therefore, perhaps it should be allowed?
R’ Cham Palagi in his sefer Chaim U’Melech (Hilchos Sotah 4:2) discusses this question. The Yalkut in Eichah (remez 1009) brings a moshul [parable]: “...To what can this be compared? To a sotah who enters the courtyard of the Beis HaMikdosh, and the Kohen comes to give her the special sotah water to drink. Then he looks and sees that the sotah is his mother. He immediately gets very embarrassed, and then he turns around and screams and cries about his mothers.
From the fact that the Medrash says such a moshul, it would seem that such a thing can happen, and a son can be the Kohen to give his mother, sotah water to drink. However, see R’ Chaim Palagi inside where he refutes this proof.
The Shu”t Maharsham (4:138) also discusses this and he takes on that it’s obvious the son can’t give his mother the sotah water to drink. He writes: It’s obvious a son can’t give his mother sotah water, as we find in Sanhedrin that a son isn’t allowed to be a shliach Beis Din to hit or curse his mother. One of the things the Kohen does before giving the sotah special water to drink is he curses the sotah, therefore, he can’t do it. Especially, when it’s possible for it to be carried out by another Kohen (see also Minchas Chinuch, mitzvah 48).
[The Maharsham mentions the Medrash, and he says we can't learn from Aggadah, especially when it’s just a moshul, and it can be explained in a way there is no proof. (We could explain very simply that the truth is that the Kohen can’t give his mother sotah water to drink, and in the moshul, as soon as the son realized it was his mother he got embarrassed and left and gave the job over to another Kohen).]
Based on what we mentioned above about the lots, it would seem that the Kohen whose mother is the sotah isn’t allowed to be entered into the lots. And if he never realized it was his mother, and he was in fact selected, seemingly the lots would have to be redone.
5) i) Rashi learns (Kiddushin 27b, Sotah 28a) that the husband only needs to be clean from sin from the time his wife was warned and found to be secluded with another man, however, if he sinned before that, the sotah water still works. According to this, even if the husband was naughty like his wife when they got married, as long as from after the time she was caught secluded he behaved and didn’t sin, the sotah water will be effective.
However, the Rambam (Hilchos Sotah 2:8) learns that the husband needs to be clean from sin entirely, and even if he sinned after erusin, the sotah water doesn’t work. The Ramban also learns like the Rambam, according to this, our question returns?
ii) Rashi brings from Chazal (Berachos 63a) that if one refrains from going to a Kohen to give terumos and maasros, then in the end he will need to come to a Kohen due to his wife being a sotah. The aveirah of not giving terumas and maasros is not one which prevents the sotah water working, therefore, for such a case the sotah water works. (Chasam Sofer, Toras Moshe)
iii) The Gemara in Sotah which says: אין מזווגין לו לאדם אלא לפי מעשיו, is talking about a second marriage, however, the first time one gets married we don’t say this. According to this, the sotah water works for a first marriage, however, for a second marriage in fact it doesn’t work. (Madanay Asher)
iv) The Mishnah Lemelech (Hilchos Sotah, Perek 2) is in doubt if the sotah water works in a case where the husband does teshuvah. If teshuvah helps, then we can answer that the sotah water works in a case when the husband did teshuvah. (R’ Ben Tzion Miller, and R’ Avraham Haber)
v) Perhaps the Gemara in Sotah which says אין מזווגין לו לאדם אלא לפי מעשיו, is talking about at the beginning of the marriage, and what the Gemara means is, that if one is a tzadik he isn’t going to end up marrying a rishanta. However, as time goes on, it could be that the husband becomes more of tzadik and a better person and the wife goes along the other path and become more of a rishanta. In such a case, the sotah water would work.
6) If this question is of interest to you, I recommend looking at the sefer Gevuros Shemonim written by R’ Yosef Engel who offers eighty answers to this question. Below we will bring just two answers:
i) One’s thoughts of pigul only invalidate the korban when standing in the azorah, if however, one is standing outside the azorah when the korban mincha is being offered then his thoughts of pigul don’t make a difference. According to this, the Kohanim could arrange that when offering up the minchas sotah, the sotah stands outside the azorah. (This is R’ Yosef Engel’s fifth answer, see also Mikdosh Dovid, siman 33 who suggests this answer).
ii) Some Rishonim (Tosfos Pesochim 63a, Bava Metzia 43b, and Rashi, Menachos 2b) learn that pigul only works if one verbalizes his thoughts, and it doesn’t help to simply have bad thoughts. According to this, the Kohen could make sure that the sotah doesn’t speak. (Shu”t Nishmas Chaim, siman 186).
7) In Parshas Vayeishev (Bereishis 40:9-11), Pharaoh’s cupbearer had a dream in which he picked grapes from a vine and squeezed them into Pharaoh’s cup. In Parshas Shelach (Bamidbar 13:23), the spies cut a branch with a cluster of grapes from Eretz Yisroel and carried it back with them. (Torah Teasers)
8) Rav Shlomah Margolis (Darkei HaShleimus) suggests that the blessings are given in the singular to hint that blessing is most prevalent when there is achdus [togetherness] and the community is united as one. Alternatively, even if some of the people are not deserving of the blessings, the individuals who are will still receive them.