It is narrated from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: "Any Muslim who, on hearing the call to prayer, says Allahu Akbar, bears witness that there is no true god but Allah, bears witness that Muhammad (peace and blessings be upon him) is the Messenger of Allah, and then says: 'Allahumma a'ti Muhammadan al-wasilata wa al-fadilah, waj'alhu fi al-a'lina darajatahu, wa fi al-mustafayna mahabbatahu, wa fi al-muqarrabina dhikrah' (O Allah, grant Muhammad the Wasilah and excellence, place his rank among the most exalted, his love among the chosen ones, and his mention among those brought near) - intercession becomes due for him on the Day of Resurrection."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 9754