“Wa-idh qāla rabbuka lil-malāʾikah”
“And when your Lord said to the angels…” (al-Baqarah 2:30, excerpt)
“Wa-idh qāla Mūsā li-qawmih”
“And when Moses said to his people…” (al-Baqarah 2:54, excerpt)
Some grammatical analyses supply an unspoken governing verb such as “remember” (udhkur) before “idh.” This can be a helpful gloss, but the standard narrative idiom can also be readily understood without insisting upon a hidden word every time.
The proposed governor belongs to grammatical explanation. It must not be confused with an assertion that a word has gone missing from the transmitted revelation.
Omission of a preposition before ‘an’ concerns an understood connective relation. This differs from omitting the entire response to a conditional ‘law’. The form and the scale of ellipsis must be kept distinct.