Berachot 14a

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 The Sages learnt {in a brayta}:

If he was reading kriyat Shema and he met his Rabbi or one who is greater than him, during the breaks he may inquire {=greet} because of honor and, it needs not be stated, he may answer. And in the middle, he may inquire because of fear, and , it needs not be stated, he may answer. These are the words of Rabbi Meir.

Rabbi Yehuda says: in the middle, he may inquire because of fear and answer {even} because of honor; and in the breaks, he may inquire because of honor and may answer a greeting to any man.

And so is the halacha {like Rabbi Yehuda}.

Achai the Tanna of the school of Rabbi Chiyya asked of Rabbi Chiyya: During Hallel and the Megilla, may one interrupt {to greet someone/return a greeting}?
Do we say that since reading the Shema is a Biblical obligation and he may interrupt, then Hallel which is Rabbinical need you ask? Or perhaps publicizing the miracle is greater?
He said: You may interrupt, and there is not in this anything.

Rava said: On the days that an individual finishes the Hallel {e.g. Succot and Chanukka} between chapters he may interrupt, but in the middle of a chapter he may not. On the days that an individual does not finish the Hallel {but omits certain chapters -- such as on Rosh Chodesh} even in the middle of a chapter he may interrupt.

And the halacha is like Rava.

The days in which the 'individual' completes the Hallel -- it is written in Halachot Gedolot that it is not to specify only the individual, but even the tzibbur is called an 'individual' so long as all of Israel are not gathered together, such as on Erev Pesach, and in a matter that the Early Neviim instituted that we should say, upon each and every tzara from which all of Israel were redeemed together from.

And the days in which the 'individual' does not complete the Hallel -- [also are] not specifically the individual, but rather even the tzibbur are called the 'individual'.

This implies that one should not interrupt in them, except because of honor. For the days that the 'individual' completes the Hallel, he interrupts in them just like the law of kriat Shema, but the days in which an 'individual' does not complete [the Hallel], even in the middle of a perek he may inquire [=greet] because of honor and respond to a greeting to any person. Thus, if this were not so, he should not interrupt. From here, Rabbenu Tam za'l deduced that one needs to bless upon them even during the days that the individual does not complete them. For if one does not bless upon it at the start and end, it is like a person who reads in sefer Tehillim, and there is no conception of 'interruption' there. And this is not not like those who wrote in the name of Rashi that one should not bless on Hallel and Rosh Chodesh, because of what we say in the last perek of Taanit (daf 28b) regarding Hallel of Rosh Chodesh, that it was the minhag of their fathers in their hands, and upon a minhag we do not bless, as we say in Succah, perek Lulav vaAravah (daf 44b): Rabbi Aivo was sitting before Rabbi Eliezer bar Tzadok. They brought an aravah before him. He thrashed if but did not bless. He said 'it is a minhag'. Thus, upon a minhag we do not bless. And Rabbenu Tam za'l brought as well from this of the last perek of Taanit itself, for it is stated there: Rav visited Bavel, and saw that they recited Hallel on Rosh Chodesh. He thought to stop them from doing so. Once he saw that they skipped, he said 'we derive from this that it is the minhag of their fathers in their hands'. And if they did not bless beforehand, then before he saw them skipping, he would have known that it was simply a minhag,  since they did not bless on it. And it is farfetched to say that he was not in shul at the beginning of Hallel.

And if you still ask, how did he not know that they wished to skip, based on that which they blessed לקרות את ההלל? For had they wished to finished it, they would have blessed לגמור! And there is to say that there is no distinction between לקרות and לגמור, for upon reading the megillah we bless al mikra megillah. And לגמור also carried the meaning of reading, just as in 'vatikin would be גומר it with sunrise' according to Rabbenu Tam. And that which they had the custom to change, sometimes saying לגמור and sometimes saying לקרות, was in order to hint to the tzibbur when they would finish and when they would skip.

And there is a further proof from Yom Tov Sheni, since it is a minhag of our fathers in our hands that we bless vetzivanu on the second day upon the blowing of the shofar and on the eating of the matzah. And it is not similar to the minhag of the arava, which is just moving it, and since it is not a takkana, it was not chashuv enough to establish for it a bracha.

And furthermore, we see in Yerushalmi: If the halacha is vacillating in your hands, see how the tzibbur acts.

And they have already practiced to bless on it.

And also, the Rif za'l wrote in Hilchot Chanuka that Hallel on Rosh Chodesh is not Biblical, but is rather Rabbinic in nature, and therefore an individual does not bless upon it. And he brings a proof from this that was learnt {in a brayta} in masechet Taanit (daf 28b): an individual does not begin, and if he began, he finishes.

And it is not a proof, according to the interpretation of the Baal Halachot Gedolot, that it specifically [a solitary person], but rather a tzibbur is called an individual so long as all Israel are not together.

And this is its interpretation: An 'individual' should not begin -- when a miracle is made for them, when not in assemblage of all Israel, he should not begin to bless the Hallel. And if he began to bless in the beginning {of the Hallel}, he should finish it as well with a blessing.

And this that it said that 'in the middle he may inquire [shalom] because of fear, our Sages were divided regarding it, in the matter of interruption in kriat Shema and in the berachot for the sake of to kaddish, kedusha, and barchu, whether or not one may interrupt. There is one who says that although one may inquire [shalom] because of fear and answer [shalom] because of honor, despite this he does not interrupt for kaddish and kedusha, for since he is engaged in praise of the Omnipresent, he should not interrupt for the sake of a different praise [of the Omnipresent]. And most of the meforshim agree that one should interrupt, even in the middle of the perek, for it is no worse that one interrupting to inquire [shalom] because of fear and answering [shalom] because of honor. And so agrees the Rabbenu Yona za'l, and he brings a proof from that which they argue later on (daf 21b) if one interrupts in tefillah {Shemoneh Esrei} for kaddish and kedusha or not.

And even though they conclude the halacha like the one who says that one does not interrupt, despite thus, since we see that in tefillah, even if the king inquires of his shalom he should not reply, and even if a snake is coiled around his ankle, he should not interrupt, and they are divided as to whether he should interrupt for kaddish or not, we may derive that in kriat Shema and berachot, where we establish that he does interrupt because of fear and answer because of honor, it is obvious to all that one interrupts.

Therefore, for kaddish, kedusha, and barchu, we interrupt even in the middle of the perek. And so do my thoughts concur, even though I dealt in depth in the matter before the Ram MiRutenberg, and his position was to conclude that one should not interrupt.

[6] [Daf 14a]
Ashian the Tanna of the school of Rabbi Ammi enquired of  Rabbi Ammi: May one who is keeping a  [voluntary] fast take a taste? Has he undertaken to abstain from eating and drinking, and this is really not such, or has he undertaken not to have any enjoyment, and this he obtains? He replied: He may taste, and there is nothing to it. 

It has been taught similarly: A mere taste does not require a blessing, and one who is keeping a [voluntary] fast may take a taste, and there is no objection. How much may he taste? —  Rabbi Ammi and  Rabbi Assi used to taste as much as a revi'it.

He may taste, and there is nothing to it: Rav Chananel za'l explained that this is such that he afterwards spits it out, and therefore this tasting is not considered benefit, and he also does not require a bracha. However, this is specifically a reviit, but more than a reviit, it is considered hanaah in terms of a fast. However it seems that a bracha he does not need, since he does not benefit within his innards.

[7] Rav said: One who gives greetings to his friend before he prays is as if he made him into a {private} altar, as it states in Yeshaya 2:22:

כב חִדְלוּ לָכֶם מִן-הָאָדָם, אֲשֶׁר נְשָׁמָה בְּאַפּוֹ: כִּי-בַמֶּה נֶחְשָׁב, הוּא. {פ

22 Cease ye from man, in whose nostrils is a breath; for how little is he to be accounted!{P}

Read not בַמֶּה {= how little} but rather בָּמָה - an altar.

And this is particularly where you {go out of your way to} go early to his door, but if you do not go early to his door, it is permitted. For we learned, in the breaks he may ask because of honor and reply to any man. {And the Shema is before the prayer, that is Shemoneh Esrei.}

Rav Yitzchak bar Ashian said: it is fobidden for a man to go on the road before he has prayed, as it states in Tehillim 85:14:

יד צֶדֶק, לְפָנָיו יְהַלֵּךְ; וְיָשֵׂם לְדֶרֶךְ פְּעָמָיו.

14 Righteousness shall go before Him, and shall make His footsteps a way. {P}

Rav Iddi bar Avin said: One who prays and afterwards sets out on the road, Hashem provides for his needs, as it states in Tehillim 85:14:

יד צֶדֶק, לְפָנָיו יְהַלֵּךְ; וְיָשֵׂם לְדֶרֶךְ פְּעָמָיו.

14 Righteousness shall go before Him, and shall make His footsteps a way. {P}

Mishna:

THE BREAKS ARE AS FOLLOWS: BETWEEN THE FIRST BLESSING AND THE SECOND, BETWEEN THE SECOND AND 'HEAR', BETWEEN 'HEAR' AND 'AND IT SHALL COME TO PASS', BETWEEN AND IT SHALL COME TO PASS' AND 'AND THE LORD SAID AND BETWEEN AND THE LORD SAID' AND 'TRUE AND FIRM'. RABBI YEHUDAH SAYS: BETWEEN 'AND THE LORD SAID' AND 'TRUE AND FIRM' ONE SHOULD NOT INTERRUPT.

There is to be uncertain if one should understand [this last phrase to mean] that he should not interrupt at all, even to respond, for it is more stringent than [even] in the middle of a perek, or perhaps this that he stated 'one should not interrupt', this is like the law of all the perakim, but it should not be considered greater than in the middle of the perek. However, it seems from the explanation of the reason, that it is because of {in Yirmeyahu} 'veHashem Elokim Emet', that one should not interrupt at all, but rather should say [the two words] 'Emet veyatziv' and then interrupt, since it will then be in the middle of the perek.