Verses of Redemption in the Megillah
There is a fairly universal custom that a number of verses from Megillat Esther are read aloud by the congregation. These verses are usually “There was a certain Jew…” (2:5), “And Mordechai left the presence of the king…” (8:15), “For the Jews there was light and joy…” (8:17), and “For Mordechai the Jew…” (10:3). This custom is probably from the Geonic period. In one of the MSS of Seder Rav Amram Gaon [1] it says that according to R. Saadiah Gaon after the reader says the first word of certain verses (it mentions all but 2:5) the congregation says the verses out loud with the reader then repeating them. While this is not in the MSS of R. Saadiah’s siddur that we have today [2], it is also attributed to R. Saadiah by a number of Rishonim. [3] This custom, although not mentioning verse 8:17, was also brought in a tradition attributed to R. Kalonymus who said that it was not an obligation, nor a custom, but rather “שמחת התינוקות” (”The joy of the children”).[4] There are a number of other variations to this custom, with some also describing the recitation by the congregation of other verses such as “On that night the king could not sleep” (6:1). [5] For some halakhists an important question to be addressed was whether the reader of the megillah should repeat these verses after the congregation recites them or not, with R. Moses Isserles ruling that the reader should repeat them.[6] Whether this custom is for the children, the adults, or both, it is one of the many interesting customs that are observed on Purim. Hag Purim Sameah.
Notes:
[1] MS Oxford, see Goldschmidt ed. pp. 101-102.
[2] See the edition by Davidson et. al., pp. 31, 257 n. 14.
[3] For a list of some of these Rishonim see R. David Yosef, Torat haMoadim: Purim veHodesh Adar, p. 197, n. 36.
[4] Sefer HaPardes, p. 254. See note 109 for parallels. Also see I.M. Ta-Shema, Minhag Ashkenaz HaKadmon, pp. 39-40.
[5] See R. David Yosef, loc. cit.; Yaakov Gelis, Minhagei Eretz Yisrael, p. 208; R. Shem Tob Gaguine, Keter Shem Tov, vol. 1, pp. 540-541.
[6] Neither the Rambam, the Tur nor R. Yosef Karo mention this custom at all, but they all mention the Talmudic custom (Megillah 16b) of reciting the ten sons of Haman in one breath. For Isserles see his comments to OH 690:17. For a list of sources discussing this question see R. David Yosef, loc. cit.