TT #63 · Parashas Noach · Fifth Aliyah · Passuk 9:27
May God enlarge Yefet, and let him dwell in the tents of Shem; and let Canaan be a slave to them.
Torah Temimah points to R’ Shimon ben Gamliel (Megillah 9b) — permission to write Scripture in Greek.
E-Daf image — Megillah 9b (size=3)
English: “May God enlarge Yefet” — It was taught: R’ Shimon ben Gamliel says: They permitted the writing of the books [of Scripture] only in Greek [besides Hebrew]. Why? Because Scripture says “May God enlarge Yefet and let him dwell in the tents of Shem” — the beauty of Yefet shall be in the tents of Shem.
Custom (permission for Greek translation of Scripture derived from the verse).
The aesthetic beauty associated with Yefet (Greek) may enter the tents of Shem — hence the unique permission to write sacred books in Greek.