In Saudi Arabia, the most influential religious authority, the Senior Ulema Council, has determined that Islamic terrorism, and contributing money to terrorists, is sinful, and a crime in a country that is governed by Sharia (Islamic law.) This is a big deal, because the Senior Ulema Council is one of the major religious authorities in the Islamic world. There is no central religious authority for Moslems, but a handful of such councils have enormous influence on all Moslems.
Some Moslems, and particularly Islamic radicals, ignore the Senior Ulema Council, because that organization consists of government employees. That's because Saudi Arabia pays nearly all clergy, and provides financial support for mosques and religious schools. Despite that support, the Saudi clerics are widely respected because they are learned and devout, despite being on the state payroll.