Musannaf Ibn Abi Shayba 2:248

Abu Bakr narrated to us, he said: Abu al-Ahwas narrated to us, from Abu Hamzah, from al-Hasan, who said: When you hear the caller to prayer (mu'adhdhin), say as he says. When he says, "Hayya 'ala al-salah" (Come to prayer), say, "La hawla wa la quwwata illa billah" (There is no power and no strength except by Allah). When he says, "Qad qamat al-salah" (The prayer has been established), say, "Allahumma rabba hadhihi al-da'wati al-tammati wa al-salati al-qa'imati, a'ti Muhammadan su'lahu yawma al-qiyamati" (O Allah, Lord of this perfect call and established prayer, grant Muhammad his request on the Day of Resurrection). No man will say it when he (the caller) establishes the prayer except that Allah will admit him into the intercession of Muhammad, may Allah bless him and grant him peace, on the Day of Resurrection.