Commentary for Berakhot 51:1
אקמטרא ככלי בתוך כלי דמי. אמר רבי יהושע בן לוי ס"ת צריך לעשות לו מחיצה עשרה מר זוטרא איקלע לבי רב אשי חזייה לדוכתיה דמר בר רב אשי דמנח ביה ספר תורה ועביד ליה מחיצה עשרה אמר ליה כמאן כרבי יהושע בן לוי אימר דאמר רבי יהושע בן לוי דלית ליה ביתא אחרינא מר הא אית ליה ביתא אחרינא אמר ליה לאו אדעתאי:
spread over a chest [containing sacred books] is regarded as a receptacle within a receptacle. R. Joshua b. Levi said : For a scroll of the Torah it is necessary to make a partition of ten [hand breadths]. Mar Zotra paid a visit to Rab Ashe's house, and saw the sleeping accommodation of Mar b. Rab Ashe, whereby a scroll of the Torah was lying and for which he had made a partition of ten handbreadths. He asked him, "According to whose opinion [hast thou done this]?" "According to R. Joshua b. Levi." "Under which circumstances did R. Joshua b. Levi say that ? When there is no other room ; but the master has another room !" He said to him, "I did not think of that."
Tosafot on Berakhot
And this ruling that there must be a partition in the room was said specifically for a sefer Torah. And also for chumoshim1Tosfos is talking about chumoshim that are written sefer Torah style on parchment and wrapped around a post. They are called chumoshim because they only contain one of the five s’forim of the Torah, not the complete Torah. Tosfos is not referring to the printed chumoshim that we use today. They are like other s’forim and need only be covered. one should be stringent as with a sefer Torah, but for other books, it is sufficient to cover them with any minimal covering.2Tosfos use of the phrase בעלמא כסוי seems to mean a minimal covering. This is a bit perplexing, because we have learned that t’filin and other s’forim require a vessel within a vessel. Perhaps Tosfos is referring to the second vessel, as we have seen about the garment placed over a closet. That garment is the second vessel. It is not really a proper vessel for a sefer but it is acceptable. Perhaps that is what Tosfos means with the phrase בעלמא כסוי.