77:24 One should have a fixed time for Torah study after lunch. Exodus 35:1 tells us that Moshe gathered the people, which the Sages explain as follows: G-d told Moshe, “Gather large groups for Me on Shabbos so that future generations will learn to assemble on Shabbos in order to study Torah together” (Midrash Tanchuma). Similarly, the Jerusalem Talmud (Shabbos 15:13) tells us that Shabbos and yom tov were only given so that the Jews might occupy themselves with Torah study. Many people are preoccupied all week with their work and are unable to study Torah regularly. On Shabbos and yom tov, they are freed from their work and are able to study Torah properly. Therefore, those who work all week and do not engage in regular Torah study have a greater obligation to learn Torah on Shabbos, every person according to his individual abilities.
78:1 When we call people up for additional aliyos on Shabbos, we can call a Kohein or a Levi for the final aliyah since we have already called the requisite seven men. (As a rule, it’s advisable not to add too many extra aliyos so as not to unduly burden the congregation – Mishnah Brurah 282:5.) Similarly, we may call a Kohein or a Levi for Maftir. We may even call one Kohein for Acharon (the final aliyah) and another for Maftir since the recitation of Kaddish constitutes an interruption between them. On Simchas Torah, when we read from three Torah scrolls, we may call one Kohein for Chosson Torah (the end of the Torah), another for Chosson Bereishis (the start of the Torah), and a third for Maftir. This is permitted because each one reads from a different Torah scroll. However, when Rosh Chodesh Teves falls on Shabbos, even though we take out three Torah scrolls, if we want to call eight people up for aliyos in the first Torah, we may not call a Kohein for the eighth. This is because we will not conclude the reading in this scroll, but rather in the second Torah, when we read the section for Rosh Chodesh; then, we may call him. This is also the case with parshas Shekalim and parshat HaChodesh when they coincide with Rosh Chodesh.