تَرْمِيهِم بِحِجَارَةٍ مِّن سِجِّيلٍ
Root r-m-y: to throw, to hurl, to take aim and throw. The same root is used for the ramy (the throwing of stones) in the rite of pilgrimage.
The verb is in the imperfect, the present-continuous form. All the preceding verses were in the past tense: faʿala, yajʿal, arsala. Here the tense changes.
This is a known technique of Arabic narration: at the most critical moment of an event one passes from the past tense into the present, and the scene is brought before the eye. We do the same in English: "He got up, he went to the door, and there she is…" Here the Qurʾān leaves off narrating the event and begins to show it. The addressee is no longer receiving news; he is watching the scene.
The verb is feminine singular because its subject, ṭayr, is a generic noun; in Arabic generic nouns can be used with a feminine singular verb.
The plural of ḥajar. Ordinary stone. Not an extraordinary object but the best-known, the cheapest, the most widespread of substances.
The series of contrasts is completed here: elephant ↔ bird, army ↔ flock, weapon ↔ stone. The sūra puts no superior instrument into the other side's hand. Had it done so, one could have said "they were defeated by a stronger army". It does not.
The first view — it is a borrowing from Persian. It is said that the words sang (stone) and gil (clay) combined and were Arabised: "stone-clay", that is, stone hardened out of baked clay. This view is widely transmitted in the classical exegetical and lexicographical tradition, and most modern linguists incline in this direction as well. Put together with the preceding word, an interesting picture emerges: in this sūra of five verses two words (fīl and sijjīl) are counted as being of Persian origin. That the Qurʾān uses words that have entered the language from outside has to do with its addressees already knowing those words; the relation between Persia and Yemen and the Hijaz makes such a passage unremarkable.
The second view — it is from the Arabic root s-j-l. From this root comes sijill (a written record, a register). On this view sijjīl means "what has been written", that is, recorded, settled by decree; as though it were written upon the stones whose lot each was. There is a usage in the Qurʾān that supports this reading: "The day We shall roll up the sky as a sijill rolls up the written sheets" (al-Anbiyāʾ 21/104).
The third — a combining reading. Some accept both senses: baked clay as substance, decreed as verdict. This is not impossible in language, but it is forced; caution is called for.
On which side is the Qurʾān's own testimony? The word occurs in three places in the Qurʾān, and in all three together with "stone":
What is decisive is this: the same event is described elsewhere with a different word. Of the people of Lot it is said at al-Dhāriyāt 51/33 "stones of clay" (ḥijāratan min ṭīn). That is, within the Qurʾān itself an equation sijjīl ≈ ṭīn (clay) is established. This markedly supports the first view — the baked-clay reading. The Qurʾān's exegesis by the Qurʾān gives a clear result here.
The same connection does one more thing: it binds Sūrat al-Fīl and the story of Lot to one another through a single word. Both events end with an intervention from the sky at the moment when a community supposed its own secure order to be indestructible.
It is transmitted in the reports that the stones were the size of a chickpea or a lentil, and that each bird carried three stones (one in its beak, two in its claws). None of these details is in the Qurʾān; it is material of report, and it is not uniform within itself either. The force of the narrative comes in any case not from size but from the difference of scale.