Islam enjoins us to avoid extravagance in all things, which includes the building of mosques. In this hadith, ‘Abdullah ibn ‘Umar speaks of the stages that the construction of the Mosque of the Prophet (blessings and peace of Allah be upon him) went through. He says that at the time of the Messenger of Allah (blessings and peace of Allah be upon him), the mosque was built of bricks, which are used in construction and are made of soft clay that is dried in the sun. Its roof was made of palm branches, and its pillars were made of palm trunks that had been cut from the old garden on the site of which the mosque was built. The mosque remained as the Prophet (blessings and peace of Allah be upon him) had built it, in terms of its area and shape, and Abu Bakr did not add anything to it or take anything away from it during his caliphate. When ‘Umar ibn al-Khattab (may Allah be pleased with him) was appointed caliph, he added to its length and width, but he did not change the method of construction; rather he rebuilt it using the same construction methods as had been used at the time of the Messenger of Allah (blessings and peace of Allah be upon him), using bricks and palm branches, but he replaced the wooden pillars. Then ‘Abdullah ibn ‘Umar (may Allah be pleased with him) said: Then ‘Uthman changed it and renovated it, and improved its construction. He built its walls of engraved stones and plaster, which is used in construction and to cover walls, and he made its roof of teak, which is a high quality and valuable Indian wood, black in colour. It was said that the first one to adorn mosques was al-Walid ibn ‘Abdul Malik ibn Marwan, at the end of the era of the Sahabah (may Allah be pleased with them), but many people of knowledge refrained from objecting to that for fear of causing friction and turmoil. This hadith indicates that the Sunnah when building mosques is to be moderate and not to go to extremes in building them, so as to avoid fitnah and competing in the construction of mosques. It indicates that it is permissible to expand mosques, and to demolish them in order to expand them and rebuild them in a better way than they were initially constructed..