Sforno on Leviticus 23:24/ספורנו על ויקרא כ״ג:כ״ד

1זכרון תרועה, a remembrance of the Royal t’ruah. When jubilating toward one’s king, one employs these blasts on the trumpets or shofars to demonstrate such regard for one’s king. Compare Psalms 81,2 הרניני לאלוקים עוזנו, הרנינו!, “stir up jubilation to G’d, our strength, raise a shout!” The expression זכרון, is an allusion to the fact that on this date G’d sits on the throne of Justice remembering the deeds of each one of His subjects and evaluating them as a judge. This is why the Talmud in Rosh Hashanah 8 calls on us to recite verse 4 in the above mentioned chapter of Psalms which reads תקעו בחודש שפר בכסא ליום חגנו, כי חוק לישראל הוא משפט לאלוקי יעקב, “blow the horn on the new moon on the day the moon is veiled, on our feast day, for it is a statute for Israel a ruling of the G’d of Yaakov.” On such days we have additional reason to rejoice in the fact that He is our King, who inclines toward leniency, and is likely to find us as possessing sufficient merit to pass this examination of the way we led our lives in the year just concluded. Isaiah expresses these sentiments in referring to G’d as כי ה' שופטנו, ה' מחוקקנו, ה' מלכנו, “for the Lord is our Judge, the Lord is our lawgiver, the Lord is our King” (Isaiah 33,22)