One of the most characteristic - and stirringly evocative - symbols of Islam is the adhan, the Arabic call to prayer, dramatically intoned by a muezzin from high atop a lofty minaret. Heard once, it is never forgotten.

The use of the adhan goes back to the lifetime of the Prophet Muhammad, and is mentioned once in the Koran, in connection with the Friday assembly:

O believers, when proclamation is made for prayer on the Day of Congregation, hasten to God's remembrance and leave trafficking aside; that is better for you, did you but know. - Sura 62:9

Muslim tradition supplies the story of how the adhan came to be used to announce the times of the five daily prayers. After the emigration of Muhammad and his followers from Makkah (Mecca) to Medina-which is called the Hijra - a believer named Abd Allah ibn Zaid had a vision in which he tried to buy a wooden clapper to summon people to prayer. But the man who had the clapper advised him to call out to the people instead and to cry:

God is most great! God is most great!

I testify that there is no god but God.

I testify that Muhammad is the Apostle of God.

Come to prayer! Come to prayer!

Come to salvation! Come to salvation!

God is most great! God is most great!

There is no god but God.

According to Ibn Ishaq, the eighth-century biographer of the Prophet, Ibn Zaid went to Muhammad with his story and Muhammad, approving, told him to ask an Ethiopian named Bilal, who had a marvelous voice, to call the Muslims to prayer. As Ibn Ishaq told the story (in Albert Guillaume's translation):

When the Apostle was told of this he said that it was a true vision if God so willed it, and that he should go to Bilal and communicate it to him so that he might call to prayer thus, for he had a more penetrating voice. When Bilal acted as muezzin, 'Umar I, who later became the second caliph, heard him in his house and came to the

Apostle... saying that he had seen precisely the same vision. The Apostle said 'God be praised for that!'

Though slightly different versions of the story exist, all agree that Islam's first muezzin was Bilal. But who was this man whom the sources credit with such a key role in the nascent Muslim community?

Actually, very little is known. Bilal ibn Rabah, an Ethiopian, was born in Makkah sometime in the late sixth century, of very humble parentage, and was one of the first inhabitants of Makkah to accept the religion that a local merchant named Muhammad - the Prophet - began to preach there around the year 610.

According to Ibn Ishaq, Bilal suffered for his immediate acceptance of Muhammad's message. In fact Bilal's master, Umayya ibn Khalaf reportedly, "would bring him out at the hottest part of the day and throw him on his back in the open valley and have a great rock put on his chest; then he would say to him, 'You will stay here till you die or deny Muhammad and worship al-Lat and al-'Uzza" (pre-Islamic goddesses).

Bilal, however, would not renounce Islam and eventually Abu Bakr, later the most distinguished of the Prophet's Companions and the first Caliph, rescued him.

In 622, the year of the Hijra, Bilal also migrated to Medina and over the next decade accompanied the Prophet on all military expeditions, serving, tradition says, as the Prophet's mace-bearer and steward, but also as a muezzin revered by Muslims for his majestically sonorous renditions of the adhan .

Bilal's finest hour came in January, 630, on an occasion regarded as one of the most hallowed moments in Islamic history. After the Muslim forces had captured Makkah, the Prophets muezzin ascended to the top of the Ka'ba to call the believers to prayer - the first time the call to prayer was heard within Islam's holiest city.

There is confusion about what happened to Bilal after the death of the Prophet in 632. Abu Bakr succeeded the Prophet as head of the Muslim community, and some sources say that Bilal acted as Abu Bakr's muezzin but subsequently declined to serve his successor, 'Umar ibn al-Khattab, in the same capacity. Other authors say the Prophets death signaled the end of Bilal's career as a muezzin, and that he called the faithful to prayer only twice more in his life - once in Syria, to honor the visiting 'Umar, and a second time, in Medina, when he was specifically asked to do so by the Prophet's grandsons.

What seems clear is that at some point Bilal accompanied the Muslim armies to Syria and that he died there between 638 and 642, though the exact date of death and place of burial are disputed.

Yet if there is some disagreement concerning the hard facts of Bilal's life and death, his importance on a number of levels is incontestable. Muezzin guilds, especially those in Turkey and Africa, have traditionally venerated the original practitioner of their noble profession, and African Muslims as a whole feel a special closeness and kinship to him; he was an Ethiopian, after all, who had been exceptionally close to the Prophet, and is a model of steadfastness and devotion to the faith. The story of Bilal, in fact, remains the classic and most frequently cited demonstration that in the Prophet's eyes, the measure of a man was neither nationality nor social status, but piety.