Hadith Q1409
وَالدَّلِيلِ عَلَى أَنَّهُ لَا يُؤَذَّنُ وَلَا يُقَامُ لِلتَّطَوُّعِ، وَإِنْ صُلِّيَتِ التَّطَوُّعُ فِي الْجَمَاعَةِ
And the explanation of the evidence that there is no adhan or iqamah for nafl prayer, even if the prayer is offered in congregation.
Hadith 1409
Abu Hurairah (may Allah be pleased with him) narrates that the Messenger of Allah (peace be upon him) once went out to pray for rain, so he led us in two rak‘ahs and recited aloud, but he did not have the adhan or iqamah called.