OU HOLIDAYS VaYigdal Mosheh on Elul By Rav Mosheh Twersky HY"D

Shofar During Elul In Pirkei d’Rabi Eliezer (perek 46), Chazal say that a shofar was blown on Rosh Chodesh Elul when Moshe Rabbeinu went up to Har Sinai (for the final 40 days). This is the source for blowing shofar during the month of Elul. The text of this Chazal as brought by a number of the Rishonim (see Radal there) is with the following expression, “it was established that shofar should be blown in Elul in order so that Klal Yisrael should do teshuvah and to befuddle the Satan.”