Two weeks ago after services, a careful reader of the Siddur (prayerbook) noticed an anomaly and asked me a question about it,
“Why do we add the phrase kapparat pesha (forgiveness of sins) to the musaf amidah of Rosh Hodeshonly in Jewish leap years?”
Well friend I am glad you asked, because while I’ve also noticed the anomaly, your question inspired me to find an answer.
The paragraph in the musaf amidah for Rosh Hodesh that begins “Our God and God of our ancestors … (page 495 in Sim Shalom)” includes twelve different blessing requested for the new month. These blessings are for things like goodness, joy, gladness, and consolation. Twelve blessings for twelve months of the year. On leap years when we add a thirteenth month to the calendar, we add one more blessing to bring the number of blessings to a lucky thirteen.