Charles Ellicott Commentary Psalms 81:3

"Blow the trumpet at the new moon, At the full moon, on our feast-day." — Psalms 81:3 (ASV)

Trumpet.—Hebrew, shôphar. (Psalms 47:5). In connection with this festival psalm, the mention of the shôphar is especially interesting, as it is the only ancient Hebrew instrument whose use is still retained on solemn occasions (see Bible Educator, Vol. ii, p. 242).

In the new moon.—Standing by itself, this phrase might mean the beginning of every month , and many scholars are inclined to interpret it this way here. Others translate it as “in this month.” However, see the next Note.

In the time appointed.—This is the translation of the Hebrew word kçseh offered by many authorities. However, in Proverbs 7:20, the only other passage where the word is found, the Vulgate translates it as “after many days.” While the English margin reads “new moon,” Aquila and Jerome render it as “full moon.”

This latter meaning (“full moon”) is supported by the Syrian version, which uses keso for the 15th day of the month (1 Kings 12:32). Yet, in 2 Chronicles 7:10, the same word is used for the 23rd day. Therefore, it is thought to denote the entire period of the moon’s waning from its fullness. Consequently, it seems hardly possible that keseh, like chadesh, could mean new moon here, as some believe, especially since it is strange to find both the new and the full moon mentioned together.

Some attempt to resolve this difficulty by adopting the plural reading feast-days, following the Syriac, Chaldee, and several manuscripts, although the authority of the Septuagint opposes this interpretation. It appears, however, that the festival in question was the Feast of Tabernacles.

The word chag used here, according to Gesenius, is employed pre-eminently in the Talmud for this feast, just as it is in 2 Chronicles 5:3 and 1 Kings 8:2 . Moreover, the Jews, always holding firmly to ancient tradition, regularly use this psalm in the liturgy for the first day of Tishri.

Thus, the new moon mentioned is that of the seventh month, which in Numbers 29:1 is specifically called a day of trumpet blowing (see Note on Psalms 81:1). The full moon, then, denotes this feast (Leviticus 23:24).