Hawzah News Agency – The Prophet (SAWA), in his advice to Abu Dharr said,

إيّاكَ وكَثرَةَ الضَّحِكِ؛ فإنّهُ يُمِيتُ القَلبَ.

'Beware of laughing a lot, for it kills the heart.'

Source: Maani al-Akhbar, p. 335, no. 1