Q. Kvod Harav, I heard that there may be an issue when davening Maariv before the Z’man (night) since one has to repeat the Shema after it becomes proper night, one may transgress the prohibition of Baal Tosif or adding to the mitzvos?
A. Regarding counting repeatedly the Omer and repeating other mitzvos we wrote on question 3109 the following:
“Minchas Yitzchok (6: 45) quoting several great Chassidic authorities, relates that these Tzadikim would mention many times every day, the omer number of that day. Thus giving a different perspective to the meaning of “Temimos” or complete days. Moadim Uzemanim (7: 230) debates whether Hagr’a would maintain that you comply with the mitzva every time the count is repeated, as he maintains on eating a repetitive Kezais of matza during the days of Pesach.
Poskim maintain that there i’s usually no prohibition of Ba’al Tosif when repeating a mitzva several times. Tosafos Rosh Hashana 16b in reference to blowing additional times the shofar on Rosh Hashana or holding the Lulav several times a day in Sukos. Turei Even disagrees (ibid.)
However, Igrois Moshe (O.H. 2: 60) debates if there is a prohibition of Ba’al Tosif when davening Maariv before the z’man, if one recites the shema too early with the intent to fulfill the mitzva. He therefore stresses one should have intent not to fulfill the mitzva at that time. He also argues that Shema is essentially a part of Torah learning and there’s no prohibition to learn Torah multiple times.
(See Chavos Daas – Beis Hasofek, Safek Safeka: 20, opines, that repeating Shema twice, even within the obligated time is prohibited).
Horav Dovid Pam Shlit’a maintains that one should have in mind a conditional intention, that whichever reading of the Shema is correct, it should be considered as the mitzva. This applies only when one of the readings may not be on the correct time for reading the Shema and then one may violate the Baal Tosif prohibition.
Horav Shlomo Miller’s Shlit’a opinion is that that it is not necessary as the accepted opinion is not to be concerned with multiple repetitions of Shema.
The common minhag is that people repeat the Shema several times in the day, such as by Korbonos, before going to sleep or when donning Rabenu Tam Tefilin etc.
Rabbi A. Bartfeld as revised by Horav Dovid Pam, Horav Aharon Miller and Horav Chanoch Ehrentreu Shlit’a.