The king must have a separate book of the Law for himself

"Now it shall come about when he sits on the throne of his kingdom, he shall write for himself a copy of this law on a scroll in the presence of the Levitical priests.

Hebrew

יח וְהָיָה כְשִׁבְתּוֹ, עַל כִּסֵּא מַמְלַכְתּוֹ--וְכָתַב לוֹ אֶת-מִשְׁנֵה הַתּוֹרָה הַזֹּאת, עַל-סֵפֶר, מִלִּפְנֵי, הַכֹּהֲנִים הַלְוִיִּם.

Greek

18 καὶ ἔσται ὅταν καθίσῃ ἐπὶ τῆς ἀρχῆς αὐτοῦ, καὶ γράψει ἑαυτῷ τὸ δευτερονόμιον τοῦτο εἰς βιβλίον παρὰ τῶν ἱερέων τῶν Λευιτῶν,

• Parashah: Shoftim
• Sefer HaChinuch: 503
• Mishneh Torah: Love — Tefillin, Mezuzah, and Torah Scroll

• Deuteronomy 17:18

Enumeration and classification from BibleData. The Greek is the Septuagint reading of the same verse, carried by the source for comparison.