At the End Times people will carefully listen to Hazrat Mahdi (as)

In Damascus a village called “Harasta” will be demolished. The name Hazrat Mahdi (as) will be called in the heavens and everyone in the East and West will hear this call! Those sleeping will wake up, those standing will sit down and those sitting down will stand on their feet. (Al-Barzanji, Al-Isha'ah li-ashrat al-sa'ah, p.164-165)

This is a portent for waking up only to listen to Hazrat Mahdi (as). Those standing up will sit down and carefully listen to him. Sometimes people stand up to focus their attention; they listen either by sitting down or standing up. People also sometimes listen the conferences standing.