"The Messenger of Allah said: 'When you hear the call (to prayer), say what the Mu'adh-dhin says.'"
Sunan Ibn Majah Book 3, Hadith 15
← Previous Hadith 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.

Sunan Ibn Majah Book 3, Hadith 14 Next Hadith → 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."

Sunan Ibn Majah Book 3, Hadith 16