בְּֽנֵי־אֶפְרַ֗יִם נוֹשְׁקֵ֥י רוֹמֵי־קָ֑שֶׁת הָ֝פְכ֗וּ בְּי֣וֹם קְרָֽב׃
The children of Ephraim were as archers handling the bow, That turned back in the day of battle.
Read Kabbalistic (mystical) interpretations of Psalms 78:9: Zohar and classical Jewish mystical sources, free online.