Fields that require irrigation may be reaped - קוצרין בית השלחין
Summary:
It is אסור מדאורייתא initially to bring the עומר from a בית השלחין (and other places). Therefore (even though בדיעבד it is כשר if the עומר was brought from a בית השלחין) it is permitted to reap the grain in those places before the קצירת העומר. There are other instances, such as by קדשים, where we find even in דאורייתא a difference between (where it is required) לכתחלה and בדיעבד (it does not matter).
However they are not to stack the grain - אבל לא גודשין
Summary:
קצירה is permitted on account of פסידא. By גדישה where there is no פסידא it is (אסור (מדרבנן because of the concern שמא יבא לאכלו. Nevertheless for עולי רגלים the חכמים relaxed this גזירה (according to ר"י) and permitted even קמח וקלי. Relaxing a גזירה because of פסידא would indicate that a גזירה should also be relaxed in order to perform a מצוה (such as ביעור חמץ).
He wraps a hollow belt around it - כורך עליו פונדא
Summary:
According to ר"י, one is permitted to tie the פונדא (with a knot) around the torn חבל; however one is prohibited from making a bow with the two ends of the חבל.
