If a person hears the Adhan (call to Prayer) while they are reciting Qur'an, should they proceed with their recitation or repeat what the Mu'adhin (caller to Prayer) says?
When the Mu'adhin makes Adhan it is Mustahab (desirable) for whoever hears him to repeat what he says. Only when the Mu'adhin says the Hay`alatayn (Statements said while making call to prayer: "come to Salah" and "come to success"), a person should say: La Hawla Wa-la Quwwata Illa Billah (there is neither might nor power except with Allah). However, if a person hears Adhan while they are reciting Qur'an; they should stop the recitation, repeat what the Mu'adhin says, then resume their recitation. The foregoing is supported by a Hadith in which the Prophet (peace be upon him) said:
When you hear the Mu'adhdhin, repeat what he says, then invoke a blessing on me, for whoever invokes a blessing on me will receive ten blessings from Allah; then beg from Allah al-Wasila for me, which is a rank in Jannah (Paradise) fitting for only (Part No. 5; Page No. 76) one of Allah's servants, and I hope that I may be that one. If anyone who asks that I be given the Wasila, he will be assured of my intercession.
Moreover, the Prophet (peace be upon him) said:
Whoever says upon hearing the Adhan: "O Allah, Lord of this perfect Da`wah (call) and of the established Salah Prayer, grant Muhammad the Wasilah and superiority, and raise him up to a praiseworthy position which You have promised him", it becomes incumbent upon me to intercede for him on the Day of Resurrection.
May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.