The discussion in Parashat Beha’alotekha concerning the trumpets opens the door to an understanding of the sounding of the shofar on Rosh Ha-shana.
According to one opinion in the Gemara, at the end of Rosh Ha-shana, the unit discussing the trumpets serves as the model from which we deduce the laws of sounding the shofar on Rosh Ha-shana.
The Gemara in Rosh Ha-shana 34b cites Rabba's famous words:
"Rabba said:
The Holy One, blessed be He, said:
Declare before Me, on Rosh Ha-shana, the malkhuyot, zikhoronot, and shofarot.