fa-alqā
So he threw
REM – prefixed resumption particle fa + V – 3rd person masculine singular (form IV) perfect verb
Root Link: ل ق ى
ʿaṣāhu
his staff
N – accusative masculine noun + PRON – 3rd person masculine singular possessive pronoun ha
Root Link: ع ص و
fa-idhā
and suddenly
CONJ – prefixed conjunction fa (and) + SUR – surprise particle
Root Link: ا ذ ا