<m.Shabbath 18.1>  

One may clear away even four or five baskets of straw or produce [grain] to make room for guests or on account of the neglect of the Beth Hamidrash, but not the store. One may clear away clean Terumah, dem`Ai, the First Tithe whose Terumah has been separated, redeemed Second Tithe and hekdesh, and dry lupines, because it is food for goats. But [one may] not [clear away] tebel, the First Tithe whereof Terumah has not been taken, unredeemed Second Tithe or hekdesh, lof or mustard. R. Simeon b. Gamaliel [T1 or T4] permits [it] in the case of lof, because it is food for ravens.

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