Is Oil considered to be a Barrier which prevents Water from reaching the Skin when making Wudhu"?

Question :

A Muslim brother asks: "I heard one of the elder scholars saying that oil is considered to be a barrier over the skin when one is making ablution, and sometimes when I am cooking, some drops of oil splash on my hair and on the parts of the body that are washed in Wudhu'; and it is necessary for me to wash them with soap before making Wudhu' or Ghusl, so that the water reaches my skin. I also put some oil on my hair, as a treatment for it. What should I do? I request your help."

Answer:

Before answering this question, I would like to make it clear that Allah, the Almighty, the All-Powerful says in His Book:
O you who believe! When you intend to offer As-Salat (the prayer), wash your faces and your hands (forearms) up to the elbows, rub (by passing wet hands over) your heads and (wash) your feet up to the ankles.

The order to wash the limbs and wipe over certain parts necessitates the removal of anything which prevents the water from reaching the skin, because if there is present anything which prevents the water from making contact with it, he will be considered to have washed it, and based upon this, we may say: If a person uses oil on the parts of his body which are cleansed during Taharah, either it will remain hard - in which case, there is no alternative to its removal before cleansing his limbs and if the oil remained thus, thick upon the skin, it would prevent the water from making contact with the skin, and the ablution would not be correct... or, the oil is not thick, and leaves only traces upon the limbs which are washed during ablution, and this does not harm. However, in this situation, a person should make sure by rubbing his wet hand over the parts to be washed, because usually the oil will show up with water, and it might be that the water does not reach all of the parts to be cleansed.

So we may say to the questioner: If this oil which is on the limbs to be cleansed is dried and prevents water reaching the skin, then he must remove it before making ablution; and if it is not thick, then there is no harm in making ablution, and there is no need to wash it with soap, but rub your hands over your limbs when washing, so that the water does not slide over it. And Allah knows best.

Source:
Ibn 'Uthaimin
Fatawa Islamiyah, Vol. 2 Pages 83-84