Purity: Requirement of Removing Grease Before Purification with Water
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 170
If a utensil or a body is impure and afterwards it becomes greasy such that water is prevented from reaching it, in the event that one wishes to wash the utensil or the body with water, he must first remove the grease so that water can reach it.
-Ayatullah Sistani, Practical Laws of Islam, Purification (Taharah)