Quba Mosque is the first mosque built in Islam, and the first mosque built in the Prophet’s city. In terms of priority, the Grand Mosque is the first house built for people and Quba Mosque is the first mosque built by Muslims, and it is also the largest mosque in the city after the Prophet’s Mosque. The mosque is located to the south of Medina. The mosque was built by the Prophet Muhammad, may God’s prayers and peace be upon him, when he migrated from Mecca to Madinah. After him, Muslims were interested in building the mosque during the past ages. Al-Waleed bin Abdul-Malik, and the succession of the caliphs after them to expand and renew its construction; Sultan Qaitbay expanded it, then the Ottoman Sultan Mahmud II and his son Sultan Abdul Majeed I followed him, until the last expansion was during the era of the Saudi state. King Fahd bin Abdulaziz Al Saud laid the foundation stone for the final expansion of the mosque in 1405 AH, and the expansion works ended in 1407 AH. The area of the prayer hall alone reached 5,000 square meters, and the area occupied by the mosque building with its service facilities reached 13,500 square metres. It can accommodate 20,000 worshippers. The Medina Development Authority is preparing to start the expansion project of the Quba Mosque and the surrounding area, to accommodate the increasing numbers of pilgrims and visitors, and to develop the area around it, urban and environmental. After the expansion is completed, the Quba Mosque is expected to accommodate 55,000 worshipers. The doors of the Quba Mosque are open all day, starting from the night of Rabi` al-Akhir 14, 1440 AH, in implementation of the directives of King Salman bin Abdulaziz. The Quba Mosque has great merit, as it was mentioned in the words of the Prophet Muhammad: Whoever purifies himself in his house, then goes to the Quba Mosque and prays in it, he will have the reward of Umrah, as it was reported in Sahih Al-Bukhari and Sahih Muslim that the Prophet used to come to Quba Mosque every Saturday, walking and riding, and praying two units of prayer in it.