All the Believers toiled in high spirits, and to quicken their task by working in measure, the masons sang in chorus, and the verses of their chants related to their exalted hopes. When the walls were seven cubits high, the Faithful covered the building with a flat roof, made of palm-tree trunks, thatched with lathes and palm-leaves. On this, they spread a layer of beaten earth, thick enough to prevent rain filtering through. The ceiling was supported inside by columns of date-tree trunks, and the floor was sprinkled with gravel. The building was one hundred cubits in length; its breadth being a little less. It could be entered by three doors; of which the principal was called "Bab-ur-Rahma," or "Door of Mercy." The "Mimbar," or pulpit, was fashioned out of a simple palm-tree trunk on which the Prophet mounted when he preached his sermons. It can thus be seen that this first Mosque, identical with those of the poorest villages of the Sahara, was far from resembling the marvellous edifices which were to be constructed a little later for the Islamic religion. At the same time as the Mosque was being finished, Mohammad had caused two little hovels to be built with clods of earth--"Hujrah"--leaning against the walls of the temple. The Prophet proposed to live there with his family and he sent Zayd, his adopted son, to Makkah to fetch them. When the houses were finished, he left the dwelling of Abu Ayyub and settled down with his people who lost no time in arriving. As for the Muhajirun, they had all been generously and hospitably welcomed by the Ansars, proud and joyful to receive beneath their roof-trees those of the strangers who fell to them by lot. Mohammad was especially moved by the cordial welcome extended to his fellow-countrymen by his new disciples. But, with his great insight concerning the souls of mortals, he resolved to tighten the bonds of such touching friendship. So that it should be proof against all insinuations dictated by the rivalry, inevitable in the future, between the Muhajirun who had forsaken their country, families and wealth to follow him; and the Ansars who had offered the safe shelter and material assistance to which his triumph was due. Would not each party have some little reason to claim for it alone first rank in the Prophet's affection and the annals of Islam? In order to avoid such dangerous contingencies and create real family ties for the exiles, Mohammad profited by the cloudless exaltation uniting Muhajirun and Ansars just then, to issue a decree of perfect brotherhood between them. He ordained that they should pair off in couples consisting of a man of the Mohajirun and an Ansar. 'Fraternise in Allah!' he told them. 'Ye are brothers!' Henceforward, every Mussulman of Al-Madinah had for brother a Mussulman of Makkah.