General Behavior (Kitab Al-Adab)
Dawud :: Book 41 : Hadith 4909
Narrated Abdullah ibn Mas'ud:
Salam ibn Miskin, quoting an old man who witnessed AbuWa'il in a wedding feast, said: They began to play, amuse and sing. He united the support of his hand round his knees that were drawn up, and said: I heard Abdullah (ibn Mas'ud) say: I heard the apostle of Allah (peace_be_upon_him) say: Singing produces hypocrisy in the heart.