This is the second book of the Mishneh Torah of the Rambam, Rabbi Moshe ben Maimon. Laws of the Sefer Torah, Tefillin, and Mezuzah.
This chapter explains that it is a mitzvah for every Jew to write a Torah scroll (Sefer Torah) for himself, and that the king must write two. It covers a Sefer Torah written without line markings, all the laws governing how a Sefer Torah is written and what invalidates it. It addresses an unrevised Sefer Torah or one containing three errors per page, writing the entire Torah in parts (Chumash), whether it is permissible to write a parchment for teaching children, whether it is permissible to paste a Tanakh onto a scroll, whether it is permissible to write holy writings without line markings, and the order of the prophets.