CUTTING A PIECE FOR YOURSELF
SEIF 2
One needs to cut a slice of bread for himself large enough to last the entire meal. (We already mentioned this as Rashi's explanation of the Gemara.) The Tosfos Shabbos quotes the Magen Avraham who says that not only cutting a big piece is permitted, though the rest of the week one is not allowed to do that because it appears to be gluttonous. However, all things described in Simon 170 that one may not do because it appears to be gluttonous, one is allowed to do on Shabbos. Therefore one may eat a garlic from it's head and drink a cup of wine in one gulp.
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