Why must he say them shortly before dark?

Rashi: If he will say them earlier, people will be negligent, and say 'there is time to do them later.'

Etz Yosef: He says this when there is enough time to tithe and make an Eruv.

Rav Elyashiv: Do not say that the Mishnah excludes only after dark, when it is too late to fix. Rather, it excludes also too early.

Is there a reason to tithe specifically before Shabbos?

Rashi: This refers to tree fruits that one will eat on Shabbos. Even a haphazard eating on Shabbos fixes for Ma'aser (obligates tithing before eating them).

Rav Elyashiv: Why did Rashi specify tree fruits? Do not say that we are concerned only for them, for their Ma'aser is mid'Oraisa. Rashi holds that only grain, wine and oil are mid'Oraisa! Rather, grain and vegetables require cooking or preparation before eating, and that fixes for Ma'aser. Tree fruits may be eaten Arai during the week without tithing; one is prone to forget do the same on Shabbos. This is why our Mishnah did not mention separating Chalah, for one always needs to separate it. Also, we separate it before baking the dough. Alternatively, the Mishnah discusses Chutz la'Aretz, where Chalah is only mid'Rabanan; one may eat and separate afterwards from what remains. (NOTE: Also Ma'aser of Chutz la'Aretz is mid'Rabanan! Why is it unlike Chalas Chutz la'Aretz? - PF) The Shulchan Aruch discusses Eretz Yisrael, therefore it mentions also 'did you separate Chalalah?' It seems that also Tosefes Shabbos fixes for Ma'aser. Surely this is true at the end of Shabbos. At the start of Shabbos, it seems that it fixes according to the opinion that one may eat during Tosefes Shabbos. According to Magen Avraham (267:1), who says that the Shabbos night meal must be at night, it does not fix.

Daf Al ha'Daf: R. Meir Shapiro says that Rashi mentioned tree fruits due to grapes and olives. Shabbos fixes them without entering them into the house. Grain is fixed in the granary, even without entering the house.

What Eruv is discussed?

Rashi: Eruvei Techumim and Chatzeros.

Etz Yosef citing the Rosh: "U'Fakadta Navcha" is Eruvei Chatzeros. Korban Nesan'el - the Rosh contradicts himself! He says that one need not command about Eruvei Chatzeros, for one may make them Bein ha'Shemashos! Rather, the text should say Eruvei Techumim; he fixes his residence in the place of his Eruv. Etz Yosef - he did not see the Tur, who wrote that even though one may make Eruvei Chatzeros Bein ha'Shemashos, it is good to make them during the day, therefore he asks about them. When the Gemara asked, why did it not answer so? Eravtem was taught next to Hadlakas ha'Ner, so presumably, it is forbidden Bein ha'Shemashos, just like Hadlakas ha'Ner.

Rav Elyashiv: Rashi explains like the Havah Amina, that the Mishnah refers also to Eruvei Chatzeros. In the conclusion, it refers only to Eruvei Techumim.

Why does he command 'light Ner Shabbos'? The other matters, he asks whether or not they were done!

Rashi: He can see whether or not it is lit.

Daf Al ha'Daf: The Rambam (Hilchos Shabbos 5:3) brings only 'light Ner Shabbos.' What is the reason? There is no argument! R. R. Reichman says, according to Bahag, that lighting Ner Shabbos is Kabalas Shabbos, we can explain 'did you tithe and make an Eruv? If so, light Ner Shabbos and accept Shabbos!' The only reason to ask about Ma'aser and Eruv is because he will command to light and accept, and perhaps they did not yet do these. If not for this, he could assume that they will fulfill these! Tana'im argue about Tosefes Shabbos - does acceptance of Shabbos before Bein ha'Shemashos forbid doing Isurim of Shabbos? Our Tana holds that it does, therefore one must tithe and make an Eruv before lighting. The Rambam holds that there is no Tosefes Shabbos, so one may tithe and make an Eruv after lighting, so he need not ask about them.

Daf Al ha'Daf: The Shulchan Aruch (260:2) says that nowadays, the custom is not to ask these. Be'er Heitev, citing the Bach, says that our custom is to make Eruvei Chatzeros for the entire year, so he need not ask every Erev Shabbos. Sha'arei Teshuvah says that he need not ask about Chalah [in Chutz la'Aretz], for one may eat and separate afterwards, but l'Chatchilah it is good to ask so they will separate beforehand. (NOTE: Ma'aser was decreed mid'Rabanan on Bavel and lands bordering Eretz Yisrael, but not elsewhere. - PF) When Erev Pesach is on Shabbos, and he may not leave over [Chametz that he bakes to eat on Shabbos], he must command to separate before Shabbos. Minchas Yitzchak (8:46) says that in Eretz Yisrael, one may not eat before separating, so he must ask.

What do we learn from "v'Yadata Ki Shalom Ohalecha u'Fakadta Navcha v'Lo Secheta"?

Maharsha: The Rosh and Ran imply that this is the source for all three matters. Rashi did not comment; it seems that he holds that it refers only to Ner Shabbos. The need to tithe and make an Eruv is known. What is the source that one must light Ner Shabbos? It is Shalom Ohalecha. "U'Fakadta Navcha" - you will command your household to light, and then "v'Lo Secheta." Rashi did not explain the source for Ner Shabbos; he relies on above (25b) "va'Tiznach mi'Shalom Nafshi" is [not having] Ner Shabbos.

Etz Yosef citing the Rosh: "U'Fakadta Navcha" is Eruvei Chatzeros, which fixes the Naveh (residence). "V'Lo Secheta" is tithing, so he will not lack food. Korban Nesan'el - Secheta is an expression of lacking, like "Ani u'Vni Shlomo Chata'im."

Rav Elyashiv: "V'Lo Secheta" - via tithing, he will not eat Tevel on Shabbos. The Ran adds that regarding Ma'aser it says "v'Lo Sisa Alav Chet." Rashi holds that obviously, one must ask about tithing and the Eruv, lest he be unable to eat and move things on Shabbos. The Chidush is Ner Shabbos, which is merely for Oneg and Shalom Bayis.

Why must one say them gently?

Anaf Yosef: One may not instill excessive fear in his house. Amidst this, they desecrate Shabbos, and light or cook on Shabbos. Sometimes they feed to him Isur, due to fear, or he has Bi'ah with his wife when she is Nidah, for she fears to tell him that she did not immerse, due to the cold, like it says in Gitin (6b, and Rashi).

Rav Elyashiv: One might have thought that all the more so, it is good to say them in a loud voice!

What are the bottom and top?

Rashi: They are the horizon and the middle of the sky, respectively.

According to R. Yehudah, how long is Bein ha'Shemashos?

Daf Al ha'Daf: Rabah and Rav Yosef argue about whether it is the time to walk two thirds of a Mil or three quarters of a Mil. They differ by the time to walk one part in 12 of a Mil. According to the Rambam and the Bartenura, this is two minutes, which is the time for the ball of the sun to rise [or set]. We can say that they argue about whether we count from when the sun begins setting, or finishes. According to the Shulchan Aruch, they differ by about one and a half minutes. How can we explain this?! (NOTE: The Shulchan Aruch can explain like the Rambam, just they said two thirds or three quarters of a Mil because it is extremely close to this (about 15 seconds more than two thirds, or 15 seconds less than three quarters)?

When is night?

Rav Elyashiv: In practice we are stringent for 30 minutes due to Sefekos - we do not know what are considered small and medium stars, there are different opinions about the time to walk three quarters of a Mil, and we do not know when sunset begins.

What is R. Yosi's opinion about Bein ha'Shemashos?

Tosfos: A Tosefta [about a Zav who had an emission Bein ha'Shemashos] proves that also R. Yosi is unsure if it is totally day, or totally night, or partially day and partially night.

Rav Elyashiv: Our Mishnah says that one cannot know the exact moment! The Tosefta is a different understanding of R. Yosi.