SHAFAQNA – The Grand Ayatollah Makarem Shirazi answered questions about religious rulings.
Question: Why religious scholars (Maraje’a) issue rulings based on precaution? For example they say according to precaution, perform Salaat again. Isn’t the religion complete?
The Grand Ayatollah Makarem: The religion is complete, but sometimes documents to prove a minor question (problem) is not completely obvious, and in these cases, the ruling is based on precaution.
Source: PERSIAN SHAFAQNA