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.  

أَنَّ مَسْجِدَ النَّبِيِّ ﷺ كَانَتْ سَوَارِيهِ عَلَى عَهْدِ رَسُولِ اللَّهِ ﷺ مِنْ جُذُوعِ النَّخْلِ أَعْلاَهُ مُظَلَّلٌ بِجَرِيدِ النَّخْلِ ثُمَّ إِنَّهَا نَخِرَتْ فِي خِلاَفَةِ أَبِي بَكْرٍ فَبَنَاهَا بِجُذُوعِ النَّخْلِ وَبِجَرِيدِ النَّخْلِ ثُمَّ إِنَّهَا نَخِرَتْ فِي خِلاَفَةِ عُثْمَانَ فَبَنَاهَا بِالآجُرِّ فَلَمْ تَزَلْ ثَابِتَةً حَتَّى الآنَ