Ibn Majah

´It was narrated that Abu Hurairah said:` "The Messenger of Allah said: 'When the Mu'adh-dhin calls the Adhan, say as he says.'"

´Umm Habibah narrated that :` When the Messenger of Allah was with her on her day and night, and heard the Mu'adh-dhin calling the Adhan, she heard him saying what he said.

´It was narrated that Abu Sa'eed Al-Khudri said:` "The Messenger of Allah said: 'When you hear the call (to prayer), say what the Mu'adh-dhin says.'"

´It was narrated from Sa'd bin Abu Waqqas that:` The Messenger of Allah said: "Whoever says, when he hears the Mu'adh-dhin, 'Wa ana Ash-hadu an la ilaha illallah wahdahu la sharika lahu, wa ash-hadu anna Muhammadan 'abduhu wa rasuluhu, radaytu Billahi rabban wa bil-islami dinan wa bi muhammadin nabiyyan (And I bear witness that none has the right to be worshipped but Allah alone, with no partner, and I bear witness that Muhammad is His slave and Messenger, and I am content with Allah as my Lord, Islam as my religion and Muhammad as my Prophet),' his sins will be forgiven to him."

´It was narrated that Jabir bin 'Abdullah said:` "The Messenger of Allah said: 'Whoever says when he hears the call to the prayer: "Allahumma Rabba hadhihid-da'watit-tammah was-salatil-qa'imah, ati Muhammadanil-wasilata wal-fadilah, wab'athhu maqaman mahmudanilladhi wa'adtah (O Allah, Lord of this perfect call and the prayer to be offered, grant Muhammad the privilege (of intercession) and also the eminence, and resurrect him to the praised position that You have promised)," my intercession for him will be permitted on the Day of Resurrection.'"