The Messenger of Allah ﷺ as saying: Between the two adhans there is a prayer, between the two adhans there is prayer for one who desires (to offer). (Using translation from Abū Dāʾūd 1283)
قَالَ رَسُولُ اللهِ ﷺ بَيْنَ كُلِّ أَذَانَيْنِ صَلَاةٌ ثَلَاثَ مَرَّاتٍ لِمَنْ شَاءَ