Dua after hearing the adhan

Allãhumma rabba hâdhihid da’watit tãmmati, wassalâtil qâ’imati, âti muhammadanil wasilata, wal fadilata, wab-ath maqamam mahmuda nilladhi wa’dth.

O Allah, Lord of this perfect call and of this established prayer, grant Muhammad (Sallaho Alaihe Wassallam) the ‘Wasilah’ and honour and raise him to the praiseworthy position which You have promised him. (Bukhari)

Note: The reciter of this duá will gain the intercession of Rasul-ullah (Sallaho Alaihe Wassallam) on the Day of Judgement.