تَرْمِيهِم بِحِجَارَةٍ مِّن سِجِّيلٍ ٤
Sentence structure
The verbal clause تَرْمِيهِم بِحِجَارَةٍۢ مِّن سِجِّيلٍۢ describes طَيْرًا in the preceding ayah. In this clause, attached هُم is the object of تَرْمِى, بِحِجَارَةٍۢ is linked to the verb, and مِّن سِجِّيلٍۢ states the stones' material.
Ayah summary
Those birds pelted them with small stones.
تَرْمِيهِم — pelting them
Grammar: A third-person feminine-singular imperfect whose subject is the hidden pronoun «هِيَ»; attached masculine-plural هُم is its object, and the verbal clause describes the preceding طَيْرًا.
بِحِجَارَةٍۢ — with stones
Grammar: Preposition بِ governs the indefinite plural genitive noun حِجَارَةٍۢ; the phrase is linked to تَرْمِيهِم.
مِّن — of / from
Grammar: A preposition beginning مِّن سِجِّيلٍۢ; this phrase is linked to an omitted adjective describing حِجَارَةٍۢ.
سِجِّيلٍۢ — baked clay
Grammar: An indefinite masculine genitive noun governed by مِّن; the phrase states the material of the stones.