Q. What is the ruling on people whistling and clapping their hands in parties?
A. This practice appears to be taken from non-Muslims; therefore, it is not an appropriate thing for a Muslim to do. When a Muslim is joyful about something , he says ALLAHUAKBAR(ALLAH IS THE GREATEST), OR SUBHANALLAH(HOW PERFECT ALLAH IS!).
Furthermore, it is incorrect to say 'Allahuakbar' in unison with a group , as some people do. A person should say this by himself; there is no basis to saying so in unison with others.
Ibn 'Uthaymeen (Rahimahullah)
Volume 8 pg.125 Chapter: Rulings For Teachers And Students