Numeri 19:1 Halakhah: Mishneh Torah, Prayer and the Priestly Blessing & Shulchan Arukh, Orach Chayim

When the first day of the month of Adar falls on a Sabbath, the section concerning the Half Shekel (Exodus 30:11-16) is read; and the lesson from the Prophets is that relating to Jehoiadah the Priest (II Kings 11:17-12:17). When the first of Adar falls on a weekday, even on a Friday, the section concerning the Half-Shekel is read on the previous Sabbath. On the second Sabbath of the month, the section commencing "Remember" (Deuteronomy 25:17-19) is read. The lesson from the Prophets is that beginning, "I remember that which Amalek did to Israel" (I Samuel 15:1-34). What is meant by the second Sabbath? It is the Sabbath preceding the week in which the Feast of Lots occurs, even if that falls on Friday. On the third Sabbath, the section concerning the Red Heifer (Numbers 19:1-22) is read. The lesson from the Prophets is that containing the verse, "And I will sprinkle upon you" (Ezekiel 36:16-36). What is meant by the third Sabbath? That immediately preceding the fourth. On the fourth Sabbath, the section beginning, "This month" (Exodus 12:1-20) is read. The lesson from the Prophets is that beginning "In the first month, on the first day of the month (Ezekiel 45:18-46:15). The fourth Sabbath is that beginning the week in which the first of Nissan occurs, even if it falls on Friday.

If one read the parsha of Parah and stopped [at the end of the tenth verse which concludes with the words] "ha'ger ha'gar be'tocham..." ("who lives among them..."), and rolled up the Torah scroll, he must go back, open it again, and start reading from the beginning of the parsha until [the verse which concludes with the words] "tit'ma ad ha'arev" ("shall be ritually unclean until the evening"), and he must make the blessing before and after it.

Once the reader began reading from the Torah scroll, it is forbidden to speak even words of Torah, and even between one person [i.e. aliyah] and the another, and even if one already finished the parasha. And there are those who permit to "grind out" (meaning: to learn) quietly. And there are those who say that if there are ten who are listening (meaning: they are paying attention) to the Torah scroll, then it is permitted to discuss (words of Torah) (Beit Yosef in the name of Mahari"a). And there are those who permit it for those for whom Torah is their profession. And there are some who permit it for one who turns one's face away before they open the Torah scroll, who makes self appear that one does not want to listen to the Torah scroll, but rather [wants] to read [i.e. learn], and begins to read [i.e. learn]. And to read "shnayim mikrah, v'echad targum" [i.e., the practice of "reading each verse twice, and the Aramaic translation once"] during the Torah reading is permitted. And all this does not apply to Parashat Zachor and Parashat Parah which must be read since they [require a quorum of] ten [people] as [obligations] from the Torah that require one to concentrate and hear [them] from the mouth of the reader. And it is proper that for all the parshiot [throughout the year], it is fitting to be scrupulous with the reader's words and for one to pay attention and hear them from the reader.