After the adhan, Hz. Peygamber taught us to say: 'Allahumma Rabba hadhihid-da'watit-tammah, was-salatil-qa'imah, ati Muhammadanil-wasilata wal-fadilah, wab'athhu maqaman mahmudanil-ladhi wa'adtah.' Whoever says this earns Hz. Peygamber's intercession on the Day of Judgment.
اللَّهُمَّ رَبَّ هَذِهِ الدَّعْوَةِ التَّامَّةِ، وَالصَّلَاةِ الْقَائِمَةِ، آتِ مُحَمَّدًا الْوَسِيلَةَ وَالْفَضِيلَةَ، وَابْعَثْهُ مَقَامًا مَحْمُودًا الَّذِي وَعَدْتَهُ
Allahumma Rabba hadhihid-da'watit-tammah, was-salatil-qa'imah, ati Muhammadanil-wasilata wal-fadilah, wab'athhu maqaman mahmudanil-ladhi wa'adtah.
Meaning: O Allah, Lord of this perfect call and the established namaz, grant Muhammad the station of al-wasilah and superiority, and raise him to the praised station that You have promised him.
Source: Sahih al-Bukhari #614Hz. Peygamber (sallallahu aleyhi ve sellem) promised his intercession on the Day of Judgment to whoever recites bu dua after hearing the adhan. Al-Wasilah is the highest station in Paradise, reserved exclusively for one servant of Allah, and Hz. Peygamber hoped it would be for him. The time between adhan and iqamah is also a time when dua is not rejected.
اللَّهُمَّ رَبَّ هَذِهِ الدَّعْوَةِ التَّامَّةِ، وَالصَّلَاةِ الْقَائِمَةِ، آتِ مُحَمَّدًا الْوَسِيلَةَ وَالْفَضِيلَةَ، وَابْعَثْهُ مَقَامًا مَحْمُودًا الَّذِي وَعَدْتَهُ
The Prophet (peace be upon him) said: 'Whoever says when he hears the call to prayer: Allahumma Rabba hadhihid-da'watit-tammah... my intercession will be permitted for him on the Day of Resurrection.'