The Egyptian cleric expressed "strong dismay at this cowardly act," and said the perpetrators should be punished through "killing, crucifixion or chopping of limbs." He termed the Islamic State a "satanic" organization that spread corruption on earth and waged war against God.
IS had earlier posted a religious edict on Twitter saying Islam permitted burning an infidel to death, as a justification for burning Jordanian pilot Muath al-Kaseasbeh while he was still alive.
'Only God tortures by fire'
Al-Kaseasbeh's barbaric death apparently served to weaken IS' popularity, but it was not clear whether conservative clerics condemned the killing itself or the method used to end his life.
"Burning is an abominable crime rejected by Islamic law regardless of its causes," Saudi cleric Salman al-Odah wrote on his Twitter page, adding that "Only God tortures by fire."
"Even if the Islamic State says Muath had bombed, and burned and killed us, and we punished him in the way he did to us, we say, okay but why film the video in this shocking way?" Abu Sayaf, a Jordanian Salafist cleric who spent ten years in Amman's prisons, told Reuters news agency.