Tafsir of Al-Waqi'ah 56:5

That is, they are crumbled, as Ibn Abbas and Mujahid said, until they become like moistened flour (sawiq). This is derived from the "bassin" of sawiq when it is moistened. It has also been said that it means they are driven and moved from their places, derived from driving a camel (bass al-ghanam) when one drives them, and it is akin to His saying, "And the mountains are moved" (wa suyyirat al-jibal).

Zayd ibn Ali recited it as "rujjat wa bussat" (they were shaken and crushed) in the active voice, meaning they shook and crumbled. In the words of Hind bint al-Khuss, describing a she-camel in a way that indicates her pregnancy: "Her eye and her thigh are trembling (raj) while she walks and straddles."