In Shabbat 14a we find a discussion about the Rabbinic enactment that a book (sefer) renders one's hands unclean (which is itself discussed in the Mishnah Yadayim 3:5). Long ago I found a source (which I wrote down) that on 14a Rashi glosses "sefer" as referring to "all kitvei ha-kodesh -- Torah, Nevi'im and Ketuvim". But I just checked that daf and I don't see anything like that in the Rashi, which means I must have gotten that gloss from somewhere else (or it is there and I am just not seeing it for some reason).
Can anybody help me track down the source for that gloss?
To be clear, I am aware that there are extensive discussions elsewhere about the status of individual books (Esther, Kohelet, Shir ha-Shirim) and whether or not they are m'tamei et hayadayim. I am not looking for that.