Does stuffing the penis with cotton invalidate the fast? And is it necessary to perform istinja' again after removing the stick used to push the cotton into the urethra?

The majority of scholars hold that inserting an enema into the urethra does not invalidate the fast, because it is not an opening to the stomach (internal cavity) and no nourishment is obtained from it. Consequently, stuffing the penis with cotton does not invalidate the fast, all the more so. Removing the stick after stuffing the penis does not necessitate performing istinja' (washing private parts), as istinja' is only required to remove traces of impurity. One must beware of obsessive whisperings and turn away from them.