Hakimullah Mehsud told his fighters that they must strictly follow orders and cannot leave the battlefield without their commander's permission. He said cowards "will go to hell and that is a very bad place."
He spoke Tuesday to his followers over a wireless radio system.
Pakistani intelligence officials shared a recording of the speech Thursday with The Associated Press.
Pakistani forces launched an offensive in mid-October against the Taliban in South Waziristan, a semiautonomous region along the Afghan border that is believed to be the main stronghold of al Qaeda and the Pakistani Taliban.