On what do scholars base their fatwas? And do they consult other scholars (such as in medicine, economics, and politics) before issuing a fatwa, or do they confine themselves to the Quran and Sunnah? Is there an authentic hadith indicating that "religious scholars do not agree on anything unless it is correct"?

"Ahl al-Dhikr" (People of Remembrance/Knowledge) are the specialists in every field. Jurists must refer to experts in matters that require knowledge and experience in a particular field before issuing a fatwa. This is evident in books of fiqh (Islamic jurisprudence) under the terms "ahl al-basar" (people of insight) or "ahl al-ma'rifah" (people of knowledge). Those firmly grounded in knowledge refer to trustworthy experts before issuing rulings on matters they do not fully comprehend. As for ijma' (scholarly consensus), it is a binding legal proof according to the majority of scholars. It is the agreement of all mujtahid (independent reasoning) scholars of the Muslim Ummah (community) after the passing of Prophet Muhammad (peace be upon him) on a religious matter.