Ata Yetzarta

The Aruch Hashulchan ( O. Ch. 225 – 2) writes that he has always wondered why when Yom Tov, Rosh Hashana or Yom Kippur fall on Shabbos, Musaf at the end of the Bracha Emtzoies (Elokkeinu Veilokei Avoseinu – Vehasieinu) we end the bracha with קדשינו במצותיך –והנחילנו -וינוחו בו – and when Rosh Chodesh falls on Shabbos at the end of Ato Yotzarto we do not end the same, with קדשינו במצותיך –והנחילנו -וינוחו בו. The Sefardim do say so (also the siddur of the Ba’al Hatanya) . For some reason it is missing from Nusach Ashkenaz. (Must of gotten lost) The Aruch Hashulchan continues, that he personally says it and there is no reason not to say it. The truth is, that Rosh Chodesh in the week days we also don’t say קדשינו במצותיך –והנחילנו -וינוחו בו – Where as Yom Tov, R.H.& Y.K. in weekdays we do say it. It must be that Chazal had a reason why On Rosh Chodesh (weekdays & Shabbos) not to say קדשינו במצותיך –והנחילנו -וינוחו בו –. GUT SHABBOS AND CHODESH