לכבוד ידיד נפשי האהוב רבי ברוך בר-אלי שליט"א הוא אשתו וכל קרוביהם לברכה והצלחה עד בלי די!
The gemara [Kiddushin 34] says that tzitzis is a מצות עשה שהזמן גרמא because one is only obligated in the daytime. Tosfos was bothered - this is seemingly not true [no offense]. To wit - According to the opinion in the gemara that even when one is not wearing the garment it is obligated in tzitzis [כלי קופסא חייבת בציצית], this obligation applies even at night. And even according to the other opinion that one is obligated only when one is wearing the garment, if it is a garment normally worn by day [כסות יום], then he is obligated at night. So however you spin it, there is always a case where ne is obligated in tzitzis at all times. So how can the gemara term tzitzis a מצות עשה שהזמן גרמא?? [See Tosfos' answer].
According to the Rogochover Gaon in numerous place [שו"ת צ"פ ל"ו וצ"פ על הרמב"ם ציצית פ"ג ה"ז ושו"ת צ"פ החדשות ס"א], there are two aspects to the mitzva of tzitzis: 1] If one wears tzititzis he fulfills a mitzva. 2] If he wears a four cornered gamrment without tzitzis he nullifies a מצות עשה and that is assur.
When the gemara says that according to R' Shimon night is not the time for tzititzis [menachos 43a] it means that at night there is no fulfillment of a mitzva but there IS an איסור to go without tzitzis. So the halacha is as follows: If it is a garment normally worn by day then at night he will be עובר an איסור if he wears it w/o four corners and during the day he will be מבטל the mitzva and עובר the איסור. If it is a garment normally worn at night the halacha is that during the day he is not עובר an איסור but he DOES fulfill the mitzva. At night there is neither a mitzva nor an issur.
One the margin of his gemara he used these principals to answer Tosfos' question. At night there is really never a MITZVA of tzitzis, just an איסור if it is a day garment.
Ahhhhhhhhh!!!:-)
