The Messenger of Allah ﷺas saying: When the iqamah is pronounced for prayer, no prayer is valid except the obligatory prayer. (Using translation from Abū Dāʾūd 1266)
قَالَ رَسُولُ اللَّهِ ﷺ «إِذَا أَخَذَ الْمُؤَذِّنُ فِي الْإِقَامَةِ فَلَا صَلَاةَ إِلَّا الْمَكْتُوبَةَ»