Prayer in common is incontestably the most profitable; the fervour of each Believer communicating with the soul of his neighbour. "It is worth twenty-seven times more than isolated prayer," says the Prophet. It was therefore necessary to summon all Believers together every day, at the same hours fixed for the five prayers. How was the exact time of meeting to be determined? Scattered over the different districts of the city, some came too early; others too late. A consultation of the leading Moslems took place. Some were for the use of a beacon, to be lit on a commanding eminence; others suggested the blowing of a horn; and the rest proposed bell-ringing. But all these methods were rejected, because they were borrowed, from Persians, Jews or Christians. [Illustration: _The Mu'azzin's Call._] Meanwhile, Abdullah ibn Zayd arrived, and he told of a dream he had had the night before. A man attired all in green passed close to me, carrying a hand-bell. I stopped him and begged him to sell me his bell. 'What dost thou want it for?'--'To summon Believers to prayer.'--'A much better way,' he replied, 'would be to proclaim the profession of faith of Islam with all the strength of thy lungs.' The Prophet, alive to the fact that the resonance of the human voice is more capable of communicating emotion than the most perfect metal instrument of music, declared at once: 'In thy dream was truth. Go and find Bilal. His voice is powerful and harmonious. I charge thee to order him to mount to the roof of the Mosque and summon the Believers to prayers.' So Bilal, the freed negro, told to call all the Believers together, of all ranks and races, uttered from the terrace of the Mosque the cry of the Islamic soul: "_Allah is great! There is no God but Allah, and Mohammad is the Prophet of Allah! Come to prayer! Come to Salvation!_" Like exquisite perfume wafted from a priceless flask, these words in the melodious voice of Bilal and issuing from his strong lungs, resounded through the city. Echoing in all dwellings, they caused every citizen to inhale with delight the refreshing scent of prayer. Ever since, in every Mosque all the world over, it is the duty of a crier, called a "muazzin," to give this summons to prayer five times daily which he does from the top of a slender minaret erected for that purpose. [Sidenote: THE FAST OF RAMADHAN] After having decided that the human voice should be used for the call to prayer, Mohammad, when first he dwelt in Al-Madinah, continued to set forth the formal obligations of the Islamic religion.