According to R. Yehoshua ben Levi, who enacted the Tefilos?

Rashi: Anshei Keneses ha'Gedolah did.

Maharsha: They did not enact the order of 18 Berachos. That was done [at the end of Bayis Sheni] in Yavneh (Megilah 17b)! Rather, they learned from the Avos that one must fulfill "Erev va'Voker v'Tzaharayim Asichah."

Etz Yosef: In the Yerushalmi, R. Yehoshua ben Levi says 'they learned Tefilos from the Avos - Shacharis from Avraham...; Rabanan say, they correspond to Temidim.' This implies that both agree that Anshei Keneses ha'Gedolah enacted them!

Rav Elyashiv: They did not enact them for after the Churban, in place of the Temidim that they used to offer, for we say (Bava Metzi'a 28a) that we do not request rain until the seventh of Cheshvan, so the last in Yisrael can reach the Pras river (before the rain comes). The Gemara discussed whether this was in Bayis Rishon or Bayis Sheni.

Daf Al ha'Daf: The Rambam (Hilchos Tefilah 1:5) says that they were enacted corresponding to Korbanos. He brings "Erev va'Voker v'Tzaharayim Asichah" (Tehilim 55:18) - this is not based on Korbanos! Rather, even though Anshei Keneses ha'Gedolah enacted it based on Korbanos, there already was a tradition in Yisrael to pray at these times, like it says in Tehilim, and Daniel "Telasa b'Yoma Ba'ei Ba'usa" (6:14).

Below, we say that R. Yosi bar Chanina must admit that the Tefilos correspond to the Temidim - if not, how can he explain Musaf? If so, why did he say that the Avos enacted them?

Maharsha: Had the Avos not enacted them, Chachamim would not have enacted them corresponding to Korbanos.

Iyun Yakov: We cannot say that Yosef enacted Musaf when he was cast in the pit, or another leader of his generation enacted it. If so, we should pray Musaf every day! Rather, it is only on days with Korban Musaf, for it corresponds to Korban Musafim.

Rav Elyashiv: R. Yosi bar Chanina did not mean that the Avos enacted them. Rather, Chachamim enacted them because we find that the Avos prayed at these three times.

Did Avraham pray only Shacharis?

Maharsha citing Sefer Yuchsin: It seems that he prayed also Minchah and Ma'ariv. He fulfilled even Eruv Tavshilin (Yoma 28b)! Rather, we learn from each of the Avos one Tefilah that it says that they prayed. Each of the Avos was zealous according to his Midah.

Etz Yosef: Surely all the Avos prayed all three Tefilos. They guarded the entire Torah, and all mid'Rabanan laws that will be enacted. In Kidushin, we expounded this from verses! R. Yosi bar Chanina holds that Avraham enacted only Shacharis, and left 'room' for Yitzchak and Yakov to enact Minchah and Ma'ariv. R. Yehoshua ben Levi holds that they did not enact them, just they knew with Ru'ach ha'Kodesh that they will be enacted, and fulfilled them.

Note: Kidushin 82a expounds that Avraham guarded the entire Torah before it was given; he kept written and oral Torah, even Eruv Tavshilin (Yoma 28b). It is not explicit that he, or Yitzchak or Yakov, guarded all mid'Rabanan laws that will be decreed. Pesach Einayim (Chulin 5a) was unsure about this; perhaps Eruv Tavshilin is different, for it is to honor Shabbos or Yom Tov! (PF)

Is there a practical consequence of the source of the three Tefilos?

Rif (on the Ein Yakov): The Amora'im argue about whether Ma'ariv is Chovah (obligatory) or Reshus (optional). The one who says that the Avos enacted them holds that it is Chovah; just like the Tefilos that Avraham and Yitzchak enacted are Chovah, also Ma'ariv, which Yakov enacted. If Tefilah corresponds to Temidim, Ma'ariv is Reshus, for it corresponds to [burning] limbs and fats that were not consumed during the day.

Daf Al ha'Daf (27b): Also Mar'eh ha'Panim (on Yerushalmi 4:1) and Pnei Yehoshua say that the two arguments depend on each other. If Ma'ariv corresponds to burning limbs and fats, which is not Me'akev, also Ma'ariv is not a Chiyuv.

Megadim Chadashim: Below (27b), we say that Ma'ariv Ein Lo Keva, for it corresponds to limbs and fats that were not consumed during the day, [one may burn them] the entire night. Ein Lo Keva means that it is Reshus. Magen Avraham (267:1) says that on Leil Shabbos, we pray earlier than usual, for the limbs and fats had to be put on the fire during the day. One may not burn Olas Chol on Shabbos (Shabbos 24b). Mor u'Ketzi'ah there disagrees. Every day, we put the limbs on the fire during the day, and they continue burning at night! It is rare that they would not put them on the fire until night. The Rambam (Hilchos Tefilah 1:6) connotes like this, that Ma'ariv corresponds to Emurim that continue burning into the night. Pri Megadim explains that the Magen Avraham holds like Rashi, that it corresponds to what is put on the fire at night. Rashi holds that this is also from other Korbanos; sometimes there was not time to put all on the Mizbe'ach during the day. The Rambam holds that it corresponds to Emurim only of the Tamid; surely they were able to put it on the fire during the day! The words of the Gemara 'what was not consumed during the day is offered the entire night' tolerate both Perushim.

Iyun Yakov #1, Daf Al ha'Daf 27b citing Pnei Yehoshua and Melo ha'Ro'im: I say that even if the Avos enacted Tefilos, Ma'ariv can be Reshus. We say (30b) 'perhaps Chanah was different, for she was very pained.' We can say that also Yakov's heart was pained due to his many afflictions - Esav, Lavan, Dinah and Yosef. Therefore, he prayed an extra Tefilah. Midrash Tanchuma (Miketz 11-12) expounds "v'Kel Shakai Yiten Lachem Rachamim..." to teach that Yakov's many afflictions pained him, and asks how many Tefilos one must pray each day. (Note: We learn that Yakov enacted Ma'ariv from a verse discussing when he fled Esav, before the other three Tzaros! Regarding Lavan, perhaps Rivkah warned Yakov about him, and he already felt pain that he will need to stay with such a man. - PF)

Iyun Yakov #2: Yakov constantly learned Torah, more than the other Avos. One who learns constantly is exempt from Tefilah. Therefore, his Tefilah is Reshus.

Iyun Yakov: Some say that the other Tefilos are Chovah, for the Avos' lips move in the grave; Yakov did not die (Ta'anis 5b).

Pesach Einayim (27b): Yakov enacted Ma'ariv only as Reshus, amidst honor of Avraham, who did not pray Ma'ariv. R. Gamliel holds that we (later generations) accepted it as Chovah; R. Yehoshua disagrees.

Megadim Chadashim: Melo ha'Ro'im says that if the Avos enacted Tefilos, Ma'ariv is Reshus. If Tefilos correspond to Korbanos, Ma'ariv is Chovah. Even though Haktaras Emurim is not Me'akev Kaparah, if they are here, we must burn them. The Gemara refutes him! It says that Ma'ariv Ein Lo Keva, for it corresponds to Haktaras Emurim!

Iyun Yakov: If the Avos enacted the Tefilos, if one missed Tefilah, there is compensation. If they correspond to the Temidim, there is no Tashlumin - if the time passed, the Korban is Batel (cannot be offered - Tosfos 26a DH Ta'ah).

Why do they not learn from "v'Avraham Odenu Omed" (Bereishis 18:22)? The Targum says that it was Tefilah!

Rif (on the Ein Yakov): That verse does not prove that it was Shacharis. Perhaps he prayed there at other times! "Va'Yashkem... El ha'Makom Asher Amad Sham" implies that also before, he rose early to pray. If not, why did he change now? Since he was adamant to pray in the same place, presumably, he also prayed at the same time.

Here it says that Yitzchak enacted Minchah. In Yoma (28b), it says 'the Tefilah of Avraham is from when walls [that face east] darken'!

Tosfos: It was Avraham's Tefilah after Yitzchak enacted it. Tosfos ha'Rosh - alternatively, Avraham used to pray Minchah, but he did not enact it for his household until Yitzchak established it.

Pnei Yehoshua: Before the Akeidah, Avraham already guarded "Mishmarti Mitzvosai Chukosai v'Sorosai" (Bereishis 26:5), from which we expound that he kept the entire Torah, even Eruv Tavshilin. We expound that Yitzchak enacted Minchah from a verse after the Akeidah! Hash-m left room for Yitzchak to enact Minchah. It was not revealed to Avraham until Yitzchak enacted it.

Megadim Chadashim: Michtav l'Chizkiyah questioned this, for that verse was after the Akeidah! I answer that just before the verse, it mentions Hash-m's Shevu'ah to Avraham, which was at the Akeidah, and it says there "Ekev Asher Shamati b'Koli" (22:18), just like "Ekev Asher Shama Avraham b'Koli va'Yishmor Mishmarti Mitzvosai..."

Here we prove that "Sichah" refers to Tefilah from "Tefilah l'Ani... Yishpoch Sicho." In Avodah Zarah (7b), we learn from "va'Yetzei Yitzchak Lasu'ach ba'Sadeh"!

Tosfos: We find like this. In Megilah (13a), regarding "va'Yhi Omen Es Hadasah", we say that Hadasim are Tzadikim, like it says "v'Hu Omed Bein ha'Hadasim", and in Sanhedrin (93a) we say oppositely (the former verse teaches about the latter verse, that Hadasim are Tzadikim).

Tosfos (Avodah Zarah 7b): We need both verses. Each teaches about the other. If we had only "va'Yetzei Yitzchak Lasu'ach ba'Sadeh", I would say that he went to speak to a person. "Eshpoch Lefanav Sichi" (Tehilim 142:3) proves that Sichah is an expression of Tefilah. If we had only the latter verse, I would not know that it is a fixed Tefilah. The verse of Yitzchak says "Lifnos Erev", which implies that he used to do so every afternoon, i.e. Minchah.

Maharsha: 'Sichah is only an expression of Tefilah' means that here it means only Tefilah, like Re'em said about 'Na is only an expression of request.'

Here it says that Yakov enacted Ma'ariv. In Chulin (91b), it says that when Yakov reached Haran, he wanted to return to pray where his fathers prayed. It is proven there that he prayed Ma'ariv during the day. In the first Perek, we say that Ma'ariv must be [Samuch to the night Keri'as Shma, which is] after Tzeis ha'Kochavim!

Tosfos: Chachamim said that Ma'ariv must be after Tzeis ha'Kochavim. We hold like R. Yehudah, that it is after Plag ha'Minchah.

Daf Al ha'Daf citing Toras Chayim: Yakov did not pray Minchah due to Ones - the sun set early! He enacted Ma'ariv, so he could then pray an extra Tefilah to compensate for missing Minchah.

Below, we suggest that the latter Beraisa refutes R. Yosi bar Chanina. He holds like the Tana of the first Beraisa!

Tzlach: The first Beraisa does not say that the Avos enacted for all generations. Perhaps it was only for their generation!

Rav Elyashiv: The answer was that R. Yosi bar Chanina merely meant that Chachamim enacted Tefilos like we find that the Avos prayed.