The pillars of the mosque of the Prophet (ﷺ) during the life time of the Messenger of Allah (ﷺ) were made of the trunks of the palm-tree; they covered from the above by twigs of the palm-tree; they decayed during the caliphate of Abu Bakr. He built it afresh with trunks and twigs of the palm-tree. But they again decayed during the caliphate of 'Uthman. He, therefore, built it with bricks. That survives until today.