"Mom says that it is forbidden to play inside the house."
Translation:אמא אומרת שאסור לשחק בתוך הבית.
Classical Hebrew used the yiqtol (imperfect) to express a variety of modal ideas, and that modal aspect of the imperfect continued in Mishnaic Hebrew. On the latter see, Miguel Pérez Fernández, Intro Grammar of Rabbinic Hebrew, 124. In Abodah Zarah 2.3 (29b) we find a list of things that belong to gentiles that are forbidden, such as Hadrianic earthenware, אלו דברים שלגוים אְַסּוּרִין וְאִסורים אִסוּר הנאה. But modern Hebrew does modality by means of specific phrases or words, one of which is אַסוּר, cf. Mishnaic אִסּוּר, איסור "prohibition, ban." In the Jewish tradition, the manuscripts often confuse Aramaic אסיר and Hebrew אסור (see Sokoloff, Dictionary of Jewish Palestinian Aramaic [2nd edition], 67-68).