Why is this a full acceptance of Ol Malchus Shamayim?

Iyun Yakov: If he defecates, he can accept Ol Malchus Shamayim without need to interrupt to relieve himself.

Etz Yosef citing R. Yonah: In the head Tefilin, man subjugates to the Creator the Neshamah in his brain. In the hand Tefilin, man subjugates his body. Therefore, they commanded to put it next to the heart, which is the root of desires and thoughts. Via this he remembers his Creator and decreases his pleasures. When he says Keri'as Shema and prays, he subjugates his Neshamah and body. Since it says 'and pray', this implies that he must pray with Tefilin on his head.

Note: He did not explain why he must defecate first. Perhaps it is like Iyun Yakov explained (lest he need to interrupt), or in order to clean his body. (PF)

Why is it as if he built a Mizbe'ach and offered a Korban on it?

Iyun Yakov: One builds a Mizbe'ach in a clean and Tahor place for Avodah. So Keri'as Shma and Tefilah are in place of Avodas ha'Korbanos; he prepares himself in cleanliness and Taharah.

How do we learn from "Erchatz..." to Tefilah? The verse discusses [surrounding] the Mizbe'ach!

Rashi: It could have said 'Architz Kapai.' Rather, it says "Erchatz b'Nikayon" - the entire body, to teach that it is as if he immersed.

Note: "B'Nikayon" is extra; it does not mention the hands, we expound it to teach about the entire body. Alternatively, 'Architz' (Hifil conjugation) implies washing something. Erchatz implies that I myself will bathe, i.e. immerse the entire body. (PF)

Rav Elyashiv: The Gemara shows that there is an attribute to immersing before Tefilah, i.e. for one who needs to immerse (he had an emission). Surely, it does not suffice to defecate and wash! Rather, it helps that his learning is considered to be with fear (just like Tevilah removes the frivolity associated with a Ba'al Keri). This is even before Takanas Ezra, for we expound a verse!

Maharsha: We rely on the Mesorah - the only other verse with "Erchatz" is "Ach Rik Zikisi Levavi " (Tehilim 73:13), which surely discusses Tefilah. "Ach Rik" - I emptied my body (defecated) and "Zikisi Levavi" - Tefilah is Avodah of the heart (Ta'anis 2a). "Va'Erchatz b'Nikayon Kapai" - I washed my hands beforehand. The Mesorah equates this washing to washing in order to offer on the Mizbe'ach (Tevilah).

Iyun Yakov: The coming verses are "Lashmi'a b'Kol Todah u'Lesaper Kol Nifle'osecha; Hash-m Ahavti Me'on Beisecha" (Tehilim 26:7-8).

Megadim Chadashim: Ahavas Eisan brings Shemos Rabah (38:4), one might have thought that he must offer bulls and rams - "Lashmi'a b'Kol Todah", I do not request you to offer, only to thank loudly. Radal explains, this is Tefilah.

Etz Yosef: "Kapai" hints to Tefilah - "va'Yifros Kapav ha'Shamayim" (Melachim I, 8:22). One who washes for this, it is like surrounding the Mizbe'ach.

Since one need not wash, for it suffices to clean his hands with anything that cleanses, why do we bless 'Al Netilas Yadayim'?

Me'iri: Some say that we bless 'Al Netilas Yadayim' only in the morning and before a meal, when one must wash. At other times, we bless 'Al Nikayon Yadayim.' If one cleaned his hands with pebbles, and afterwards washed, he does not bless, for he was already Yotzei via the pebbles.

Note: This is like the Rambam, who holds that we bless on washing before every Tefilah. Our custom is to bless only in the morning and before a meal! (PF)

Etz Yosef: Cleansing permits Tefilah, but only water removes Ru'ach Ra (OC 4:22).

Note: He did not come to answer the question, but it seems that his words answer it; cleansing suffices only when he has no water. (PF)

Why must the womb be connected to the grave? The verse lists three matters that are not satiated!

Maharsha (Sanhedrin 92a): The Gemara asks, for regarding the third (land), the verse says that it is not satiated with water. It did not teach what does not satiate the womb and the grave (Bi'ah and Mesim, respectively). Therefore, they were taught due to their similarity. Just like the womb is a place of entry and exit... this is the Mashal of Kaiser's daughter (91a. It is harder to make Kelim out of water than out of clay. If Hash-m can make people out of a drop of semen, and all the more so He can make out of earth!) There is formation from water in the womb, in this world, and formation from mud in the grave, in the future, based on a Kal v'Chomer from formation in the womb, in this world.

Why is Gehinom cooled for such a person?

Iyun Yakov: This is Midah k'Neged Midah. Just like he separates words prone to be slurred together, and does not rush his words, they wait for him for Gehinom to cool off, like everything hot that cools over time.

Megadim Chadashim: Chafetz Hash-m says that he is totally saved from punishment in Gehinom. Derech Eretz Zuta (9; in some versions, Derech Eretz Rabah 7:20) says 'be careful with Keri'as Shma and Tefilah, to be saved from judgment in Gehinom.' Kikar l'Aden (the Chida) there explains that he is not totally exempted.

Daf Al ha'Daf citing Ateres Zekenim: This is Midah k'Neged Midah. He arouses himself and arouses his natural heat to be meticulous about the letters. The reward is to lower another heat, or Gehinom.

What kind of person is so meticulous about Keri'as Shma, and he goes to Gehinom?

Rav Elyashiv: It is not a total Tzadik, who does not go to Gehinom. However, Tzlach brings from Chachmei ha'Musar that even total Tzadikim who go to Gan Eden, they pass through Gehinom; it is cooled for them when they pass through.

Note: Some Tzadikim pass through Gehinom on their way to Gan Eden, in order to raise one who was almost ready to leave. Even Tzadikim like Moshe and R. Yochanan ben Zakai were concerned for this! See Biurei Agadah for Berachos 28:5:n:3:i. (PF)

What do we learn from reading the verse like 'b'Faresh Shakai... b'Tzalmaves'?

Rashi: If you will explicitly say Shakai and separate the words of [Ol] Malchus Shamayim, Melachim Bah (the Torah, in which kings rule) Tashleg b'Tzalmaves (will cool for you the shade of death).

Maharsha: This name (Shakai) comes out of Parashas Keri'as Shema to protect man from Mazikin, like it says (Shevu'os 15b) "Yoshev b'Seser Elyon b'Tzel Shakai..." (Tehilim 91:1). Therefore, we write it on the back of Mezuzos, opposite Parashas Shema. If one is meticulous about the letters, also in the world to come it will protect against damaging angels appointed over Gehinom. They cool Gehinom with snow, like we say that there is Gehinom of snow, and it cools Gehinom of fire.

Etz Yosef citing Semichus Zekenim: We read "b'Fares" with a Sin (spreading) like 'b'Faresh' with a Shin (make explicit, i.e. say the name properly). Shem Shakai distances Mazikin, therefore it is used to denote Keri'as Shma. Tzalmon is darkness; Tzalmaves is Gehinom. The Gemara says, do not explain simple darkness, rather, the darkness of Gehinom.

Etz Yosef citing the Aruch: When you explicitly say the letters and words in Malchus Shakai, i.e. Keri'as Shma - Melachim Bah, i.e. Gehinom, the place of kings of Ashur, will be cooled.

Rif (on the Ein Yakov): We cannot read 'b'Fares' to be spreading, for it did not say what is spread! And how will Tzalmon (darkness) be snowy - it should say that it will illuminate! Also, it should have said Laylah (if it refers to darkness)! Rather, we read b'Faresh, an expression of distinction and Hafrashah between the words of Malchus Shamayim.