ציטירנדיקער פּירוש אויף תהילים 96:12

of the field [Hebrew: s̀adai] an adjective, vocalized as in “wise” [Hebrew: ḥakham], with a yod in place of a heh (like the vav in “I was at ease” [Job 16: 12]), as evidenced by “let the field be joyful” [Psalms 96: 12], where the singular form of the verb is used.

he will not rejoice Heb. יעלס, with it. Similarly, יַעֲלֹז, and so יַעַלֹץ ; the three of them are interchangeable.

ביום הראשון, “on the first day (of the festival).” The palm frond, lulav, which we shake on that day is to symbolise the fact that we have been found deserving of atonement on the recent Day of Atonement. This is what the psalmist had in mind when he said in Psalms 96,12: אז ירננו עצי היער, “then all the trees in the forest shall shout for joy.” Who does this verse speak of? Of the Jewish people in the desert as well as the nations of the earth whom G–d had sat in judgment of on the Day of atonement, see verse 13 in the same chapter of Psalms: לפני ה' כי בא לשפוט הארץ, ישפוט תבל בצדק ועמים באמונתו, “in the presence of the Lord, for He is coming, for He is coming to rule the Earth; He will judge the world fairly and its people in faithfulness.” Both the Jewish people and the gentile nations have come up for judgment on that day, and we do not know which ones are the victors. G–d advises us to hold the lulav in our hands, so that everyone will know that we have been acquitted. Tanchuma on this verse illustrates this by a parable. Two men appear before the king for judgment. The people on the outside have no idea which one of them was successful. All they know is that if one of them holds a cane or an apple in his hand when he emerges from the palace, he is the victor. The Jewish people, being modest, waited for five days before showing that they had been the victors in their confrontation with the gentiles. (Tanchuma, section 18)