the prophet's marriage to `a'ishah muhammad was satisfied with the result of his negotiations. the muslims felt secure in their religion and began to practice its duties and precepts as individuals and groups in public, without fear of attack or harm from any source. at this time muhammad married `a'ishah, daughter of abu bakr, who was then ten or eleven years old. she was a beautiful, delicate, and amiable young girl, emerging out of childhood and blossoming into full womanhood. although she was fully grown, she was still quite attracted by amusement and play. she had a room of her own near that of sawdah alongside the mosque. in muhammad, she found not only a sympathetic and loving husband but also a compassionate father who was not at all offended by her inclination to play games and amuse herself with trifles. on the contrary, she was for him a source of relaxation from the continuous tension imposed upon him by his great burden to which the government of yathrib had just been added. adhan or the call to prayer it was during this interval in which the muslims felt secure in their religion that the duties of zakat, fasting, and legal sanctions of islam were imposed and its dominion was firmly established in yathrib. ever since muhammad arrived in madinah, whenever the time of prayer came, the people assembled around the prophet without call. it occurred to him to have the muslims called for prayer by means of a horn, following the style of the jews, but he found the idea unbecoming. he had also thought of using the clapper, in the manner of the christians. after consulting `umar and a number of muslims, according to one report, and by the command of god, according to another, he changed his idea to the adhan and commanded `abdullah ibn zayd ibn tha'labah : "get up with bilal and dictate the call to prayer to him, but let him deliver it forth for he has a more beautiful voice than yours." a woman of banu al najjar owned a house next door to the mosque which was higher than the latter. bilal used to ascend to the roof of that house and deliver the call to prayer from there. thus the people of yathrib all began to hear the call to prayer many times a day beginning at dawn. the islamic call to prayer was equally a call to islam sung beautifully by a beautiful voice and carried on the waves of the air unto all corners of the horizon. it was a call which penetrated the ear of life itself. it said, "god is greater. god is greater. i witness that there is no god but god. i witness that muhammad is the prophet of god. rise to prayer. rise to felicity. god is greater. god is greater. there is no god but god." henceforth, the muslims' fears were dissipated and they felt secure. yathrib became madinah al nabiy or "the city of the prophet." while the non-muslim inhabitants began to fear muslim power knowing well that it stemmed from the depth of hearts which had tasted sacrifice and persecution for the sake of faith, the muslims collected the fruits of their patience and enjoyed their religious freedom. there peace and freedom were now made constitutional by the islamic principles that no man has any authority over any other, that religion belongs to god alone, that service is to him alone, that before him all men are absolutely equal, and that nothing differentiates them except their works and intentions. in madinah, the atmosphere was finally cleared of all impediments, and muhammad openly proclaimed his teachings. the theater was ready and the stage was set for muhammad to constitute by his conduct the ideal exemplification and embodiment of these teachings and principles, and for his laying down the foundation stone of islamic civilization.