Anas (RA) said, the Prophet (ﷺ) said, when the call to prayer (adhan) is given, the gates of heaven are opened and the dua is accepted.
Source: Sahih (Albani). Silsila Sahihah: 1413
Duas from IslamicAPI's Masnun Dua dataset (based on the Quran, hadith, Hisnul Muslim and Rahe Belayat). See the dataset