Call to Prayers (Adhaan)

                                      Volume 1, Book 11, Number 577:

Narrated Anas:

The people mentioned the fire and the bell (they suggested those as signals to indicate the starting of prayers), and by that they mentioned the Jews and the Christians. Then Bilal was ordered to pronounce Adhan for the prayer by saying its wordings twice, and for the Iqama (the call for the actual standing for the prayers in rows) by saying its wordings once. (Iqama is pronounced when the people are ready for the prayer).

Volume 1, Book 11, Number 578:

Narrated Ibn 'Umar:

When the Muslims arrived at Medina, they used to assemble for the prayer, and used to guess the time for it. During those days, the practice of Adhan for the prayers had not been introduced yet. Once they discussed this problem regarding the call for prayer. Some people suggested the use of a bell like the Christians, others proposed a trumpet like the horn used by the Jews, but 'Umar was the first to suggest that a man should call (the people) for the prayer; so Allah's Apostle ordered Bilal to get up and pronounce the Adhan for prayers.

Volume 1, Book 11, Number 588:
Narrated Jabir bin 'Abdullah:
Allah's Apostle said, "Whoever after listening to the Adhan says, 'Allahumma Rabba hadhihi-d-da' watit-tammati was-salatil qa'imati, ati Muhammadan al-wasilata wal-fadilata, wab' athhu maqaman mahmudan-il-ladhi wa' adtahu (O Allah! Lord of this perfect call (of not ascribing partners to You) and of the regular prayer which is going to be established! Kindly give Muhammad the right of intercession and superiority and send him (on the Day of Judgment) to the best and the highest place in Paradise which You promised him)', then intercession for me will be permitted for him on the Day of Resurrection").