Daf Yomi - Yoma 69 - Sitting in a Sukkah During the Rain

The Gemora states that the kohanim were permitted to derive pleasure from their clothing in the Mikdash even when they were not performing the avodah of the Beis Hamikdosh. The Gemora in Kidushin says that this was allowed for the Torah was not given to the heavenly angels and it cannot be expected of them to remove their clothes at the precise moment that they finished the avodah.

The Rama rules that one who stays in a sukkah when it is raining is called a 'hedyot.' The Oneg Yom Tov asks that this should be forbidden completely? One is not allowed to derive any pleasure from the sukkah all seven days. A person sitting in the sukkah while it is raining is not fulfilling any mitzva and therefore is unlawfully deriving benefit from the protection of the sukkah? (If one covers the sukkah with a shlock, it is not a problem for this now becomes a sukkah pesulah.)

He concludes, based on the aforementioned Gemora that it is allowed for the Torah was not given to malachim and therefore one cannot be expected to leave the sukkah the moment it begins to rain and hence it is permitted even after that.