“ונתת על השלחן לחם פנים לפני תמיד”
The מחבר (סימן קע”א סעיף א’) brings the halacha that one may use bread for his personal needs as long as the bread will need be ruined when using it. This is the halacha of הפסיד אוכלין – the prohibition to ruin food for no reason. The מחבר continues with the halacha of ביזוי אכלים – the prohibition to disgrace food. One may not throw bread because of ביזוי אכלים. This is true even if the bread does not become ruined when throwing it. This applies to other foods as well. However the מחבר says that with other foods it is prohibited only if they will get ruined when throwing them. Foods that will not get ruined are allowed to be thrown. Only bread is prohibited to be thrown in all circumstances. This is the opinion of the מחבר. This is based on the Gemara in Berachos 50a which seems to differentiate if it gets ruined, only by other foods, not by bread.
The מחבר (סימן קס”ז סעיף י”ח) brings the halacha that the בוצע gives a piece of bread to everyone. The Mishnah Berurah says from the מגן אברהם that he should not throw the bread even if it won’t become ruined according to the halacha mentioned above. Even more so by hamotzi the פרי מגדים says, because it is also a ביזוי מצוה. It seems very clear that it is prohibited to throw the bread when giving it out to everyone around the table.
However the כתב סופר said that his father the חתם סופר would throw the bread to all the מסובין. Reb Elyashiv zt”l explains that perhaps the חתם סופר held that the whole issur to throw bread is only when you are getting rid of it. Getting rid of it in such a way is ביזוי אוכל. However if you are throwing it so someone else can eat it, that is not considered ביזוי אוכל.
The Divrei Chaim in his הגהות על שו”ע says that the psak of the מחבר is not like most ראשונים. The Gemara in Berachos says that one should not throw גלוסקאות – a type of bread, לא בימות החמה ולא בימות הגשמים – both during the summer season or rainy season. Rashi explains because they become ruined even during the summer time. The meforshim asks why Rashi gives this reason if there is an issur to throw bread even if it does not get ruined. The בית יוסף says that we see from here that Rashi understood the Gemara that there is no difference between bread and other foods, and it is only prohibited to throw if it will get ruined. This is also the opinion of the רי”ף ורמב”ם. The בית יוסף brings the מחלוקת הראשונים. The Divrei Chaim therefore says that the מנהג is to throw the bread since most ראשונים hold that there is only an issur if it will get ruined. However aבעל נפש יחוש לעצמו – if possible one should refrain from doing so.
Prepared by R’ Avrohom Yehoshua Ziskind
 Sources:בית יוסף,משנה ברורה,שיעורי ר’ אלישיב,מתיבתא