Rasulullah (Sallallahu alayhi wasallam) said:
“Laughing in the Musjid will be zulmat (darkness) in the grave.”
“Conversation in the Musjid devours good deeds just as cattle devour grass.”
Numerous among the Ulama and the Tabligh Jamaat are lamentably oblivious of the prohibition of conversing and laughing inside the Musjid. At times their talk is so loud as to be a befitting sign of Qiyaamah.
Rasulullah (Sallallahu alayhi wasallam) said that among the signs of Qiyaamah is that “voices will become loud in the Musaajid.”
The worst culprits in this misdeed are the so called people of piety –
molvis and tableeghis.
Even whilst the Athaan is being proclaimed, they continue private discussions right inside the Musjid.

Laughter and worldly talk are sacrilegious inside the Musjid.
When even reciting the Qur’aan Majeed loudly in the Musjid is not permissible when musallis are present, how can indulgence in worldly conversation and laughter ever be permissible? The total indifference in this regard renders these misdeeds kabeerah (major sins).