הלכה אויף תהילים 47:6

We may not mention malkhiot, zikhronot and shofarot of punishment — such as [in] zikhronot, "And all flesh shall remember that, etc." (Psalms 78:39); [in] malkhiot, "with outpoured anger shall I rule over you" (Ezekiel 20:33); [and in] shofarot, "Blow the shofar on the mountain, etc." (Hosea 5:8). Nor [may we mention] the remembrance of an individual — even if it was for good — such as "Remember me, O Lord, in the desire of Your people" (Psalms 106:4); and "Remember me, my God, for the good" (Nehemiah 13:31). And recollections (pikdonot) — such as "I have surely recalled you" (Exodus 3:16) — are not the same as remembrances. But one may mention the punishment of idolatrous nations, such as "The Lord reigned, nations tremble" (Psalms 99:1); "Remember the day of Jerusalem to the Children of Edom" (Psalms 137:7); [and] "the Lord, God, will blow with the shofar, and go in the storms of the south" (Zechariah 9:14). All of these verses: "Hear Israel, the Lord, our God, the Lord is one" (Deuteronomy 6:4); "You have been shown to know" (Deuteronomy 4:35); "And you shall know today and place upon your hearts, etc." (Deuteronomy 4:39) — their content is kingship. Even though there is no mention of kingship [in them], it is surely like, "The Lord will reign forever and ever" (Exodus 15:18); [and] "And then He became King in Jeshurun, etc." (Deuteronomy 33:5).

And we are accustomed to blow the shofar in all the places of Israel on the first day of Elul. And this custom is supported in the Midrash. And likewise is it written in several Aggadot: On the first day of Elul, Moshe ascended the mountain to receive the second tablets, so they blew the shofar in the whole camp - behold Moshe ascended the mountain - so that they should not err in idolatry anymore. And the Holy One, blessed be He, ascended with this blow and with that shofar, as it is stated (Psalms 47:6), God arose with the teruah; the Lord with the sound of the shofar." So our Sages, may their memory be blessed, accordingly established that they should blow the shofar on the first day of Elul every year. And we are accustomed to say, Avinu Malkenu (our Father, our King) after the morning service and the afternoon service, even on Shabbat.

Before one blows one makes the blessing "to hear the sound of the shofar" and makes the blessing "shehecheyanu." Rema: And there is no distinction between blessing for oneself or if one has already fulfilled [the obligation of blessing] and blesses to fulfill the obligation of others. Either way, the one blowing makes the two aforementioned blessings (based on Beit Yosef and Trumat HaDeshen). And one blows Tekiyah Shevarim Truah Tekiyah three times; and Tekiyah Shevarim Tekiyah three times; and Tekiyah Truah Tekiyah three times. Rema: And it's best to blow on the right side if possible to blow this way (Minhagim). And also to direct the shofar upwards as it is said "Raise up G-d with the shofar" (Rokeach and Maharil).