Although Rosh Chodesh was yesterday, I saw an interesting Halacha that I wanted to share:
The Jewish religion has been blessed with the opportunity to speak to G-d three times a day (Shacharis, Mincha, and Maariv). There are days however, where we have the privilege to be in prayer more than 3 times a day. These days are of course the Yomim Tovim and alike that demand that we pray the additional prayer of Mussaf (redundant).
One of these days is the holiday of Rosh Chodesh. Rosh Chodesh was the first commandment that was officially given to Klal Yisrael. Moreover 2,000 years later, in Eretz Yisrael, during the Syrian-Greek persecution, Rosh Chodesh was one of three commandments that the persecutors deemed to be prohibited in practice. The other two being the Sabbath and Circumcision.
Due to the holiday’s uniqueness at its core, in praise and thanks to G-d, we add Yaaleh viyavo during the Shmoneh Esrei and an extra prayer after Shacharis known as Mussaf.
Halacha dictates that if one forgot to say Yaaleh Viyavo during the Morning Prayer he must return and repeat the Shmoneh Esrei.
What would be the case however, if one remembered that he did not say Yaale Viyavo for the Morning Prayer after already reciting Mussaf?
The Chofetz Chaim says in his work the Mishna Brura (422:4), that one should repeat the Shacharis Shmoneh Esrei while stipulating (before hand) that in case the Shmoneh Esrei is not obligatory that it be considered a Tefillas Nidavah, a voluntary blessing.