The mosque (of the Prophet) during his lifetime was built with bricks, its roof with branches of the palm-tree, and its pillars with palm-wood, as Mujahid said: Abu Bakr did not add anything to it. But 'Umar added to it; he built as it was built during the lifetime of the Messenger of Allah (ﷺ) with bricks and branches, and he changed its pillars. Mujahid said: Its pillars were made of wood. 'Uthman changed it altogether with increasing addition. He built its walls with decorated stone and lime. And he built the pillars with decorated stone and its roof with teak. Mujahid said: Its roof was made of teak.

Abu Dawud said: Al-Qassah means lime used as mortar.