Charles Ellicott Commentary Judges 9:27

"And they went out into the field, and gathered their vineyards, and trod [the grapes], and held festival, and went into the house of their god, and did eat and drink, and cursed Abimelech." — Judges 9:27 (ASV)

And made merry. —The vintage was the most joyous festival of the year (Isaiah 16:9–10; Jeremiah 25:30). The word rendered “merry” is hillûlim, and occurs only here and in Leviticus 19:24, where it is rendered “ praise.” Some render it “offered thank-offerings.” The Chaldee renders it “dances,” and the Vulgate “choirs of singers.” The word evidently involves the notion of triumphant songs (Septuagint, elloulim and chorous).

Of their god. —Baal-berith.

Did eat and drink. —In some public feast, such as often took place in idol temples (Judges 16:23; 2 Kings 19:37; 1 Corinthians 8:10). It is evident that this was a sort of heathen analogue of the Feast of Ingathering. The apostasy would be facilitated by a transference of customs of worship from Elohim to Baal.

Cursed Abimelech. —Rather, abused. This seems to have been the first outburst of rebellion among the general population, and Gaal took advantage of it.