Commentary for Psalms 78:9

The sons of Ephraim who left Egypt forcefully before the end [of the exile] and trusted in their might and in their arrows. Ultimately, they retreated and fled on the day of battle, as is delineated (I Chron. 7:21): “and the men of Gath, who were born in the land, slew them.”

archers Heb. רומי, who cast and shoot, as (Exod. 15:1): “cast (רמה) into the sea.”