(72) باب إِعْلاَنِ النِّكَاحِ بِالصَّوْتِ وَضَرْبِ الدُّفِّ .
It was narrated that Abu Balj said:
"I heard Muhammad bin Hatib say: 'What differentiates between the lawful and the unlawful is the voice (singing).'"
Reference: Sunan an-Nasa'i 3370
In-book reference: Book 26, Hadith 175
English translation: Vol. 4, Book 26, Hadith 3372