Sayyiduna Anas bin Malik (may Allah be pleased with him) relates that the Prophet (peace and blessings be upon him) said: "When you hear the mu'adhdhin, say the words that he says."
Imam al-Bazzar recorded this narration, and he says: Hafs bin Ammar al-Tahi is alone in narrating it, and no one has corroborated him in it.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الصلاة / 1868