"The use of oil is symbolic. It’s meant to demonstrate that the person being prayed for is being set apart for a divine purpose."
Read Is Anointing with Oil Proper, by Jack Kelley, at Grace thru Faith.
Then you shall take the anointing oil and pour it on his head and anoint him.
"You shall invite Jesse to the sacrifice, and I will show you what you shall do ; and you shall anoint for Me the one whom I designate to you."
1 Samuel 16:3
And they were casting out many demons and were anointing with oil many sick people and healing them.
Is anyone among you sick? Then he must call for the elders of the church and they are to pray over him, anointing him with oil in the name of the Lord;