Sheik Ahmed el-Tayeb also called for the transitional period that began following last week's ouster of the president to be limited to six months.
In a statement he says he will go into seclusion until "everyone shoulders his responsibility to stop the bloodshed, instead of dragging the country into civil war."
El-Tayeb is the grand imam of the Al-Azhar Mosque, the world's primary seat of learning for Sunni Muslims, the vast majority of the world's Muslims.
El-Tayeb's Monday statement came hours after clashes between security forces and supporters of the ousted president Mohammed Morsi left at least 42 killed.
