Many significant halakhot can be learned from the custom of hallel based on the manner in which it was recited. In reciting hallel there are allusions to several halakhic matters and customs that the Sages instituted due to circumstances extant at the time. Although due to increased literacy and familiarity with the hallel liturgy the reasons no longer apply, these customs remain in practice. The prayer leader recites: “Halleluya” (Psalms 113:1), and the congregation recites: Halleluya, in response. From here is the source that there is a mitzva to respond: Halleluya.

Likewise, the prayer leader recites: “Give praise, servants of the Lord” (Psalms 113:1), and the congregation recites: Halleluya, in response. From here is the source of the halakha cited in the mishna that if an adult male was reciting hallel on his behalf, he answers: Halleluya. He recites: “Thank the Lord, for He is good” (Psalms 118:1), and they respond: “Thank the Lord, for He is good.” From here is the source that there is a mitzva to respond by reciting the beginnings of chapters. It was also stated that Rav Ḥanan bar Rava said: There is a mitzva to respond by reciting the beginnings of chapters.

Rava continued to cite the significant halakhot learned from hallel. The prayer leader recites: “Lord, please save us” (Psalms 118:25), and the congregation recites: “Lord, please save us,” in response. From here is the source of the halakha cited in the mishna that if a minor was reciting a portion that is not from the beginning of a chapter on one’s behalf, he recites after him precisely what he says.

The prayer leader recites: “Lord, please grant us success,” and the congregation recites in response: “Lord, please grant us success” (Psalms 118:25). From here is the source of the halakha that if one comes to repeat a particular verse in hallel twice, he may repeat it. The prayer leader recites: “Blessed is one who comes” (Psalms 118:26), and the congregation recites the rest of the verse: “In the name of the Lord” (Psalms 118:26), in response. From here is the source of the halakha that the halakhic status of one who hears a passage recited is equivalent to that of one who recites it, as the congregation fulfills its obligation even though it does not repeat the entire verse.

Apropos this halakha, the Gemara relates that the Sages raised a dilemma before Rabbi Ḥiyya bar Abba: If one heard a passage recited and did not recite it himself, what is the halakha? Did he fulfill his obligation or not? He said to them that the Sages, and the schoolteachers, and the heads of the nation, and the homiletic interpreters said: One who heard a passage recited and did not recite it himself fulfilled his obligation.

It was also stated that Rabbi Shimon ben Pazi said that Rabbi Yehoshua ben Levi said in the name of Bar Kappara: From where is it derived that the halakhic status of one who hears a passage recited is equivalent to that of one who recites it? It is as it is written: “All the words of the book which the king of Judea has read” (II Kings 22:16). And did King Josiah read them? Didn’t Shaphan read them, as it is written: “And Shaphan read it before the king” (II Kings 22:10)? Rather, from here it is derived that the halakhic status of one who hears a passage recited is equivalent to that of one who recites it, and it is as though Josiah read the words himself.

The Gemara asks: And perhaps after Shaphan read them Josiah read them again? Rav Aḥa bar Ya’akov said: It should not enter your mind to say so, as it is written: “Because your heart was tender and you humbled yourself before the Lord when you heard what I spoke in this place” (II Kings 22:19). The Gemara infers: “When you heard” is written in the verse, and not: When you read. In other words, immediately upon hearing Shaphan read the text, King Josiah sent for Huldah the prophetess, which shows that he humbled his heart. Clearly, the halakhic status of one who hears a passage recited is equivalent to that of one who recites it.

Apropos hallel, the Gemara cites additional halakhot. Rava said: Let a person not recite: “Blessed is one who comes,” and then, after pausing, recite: “In the name of the Lord.” Rather, let him recite without pause: “Blessed is one who comes in the name of the Lord.” Rav Safra said to Rava: