Psalms 133:1-2
Behold, how good and how pleasant it is
For brethren to dwell together in unity!
It is like the precious oil upon the head,
Running down on the beard,
The beard of Aaron,
Running down on the edge of his garments.

Anointing oil is not found in all churches of Christianity, but it should!
Much is said of anointing throughout the Bible, including the New Testament.
Right before I resigned a pastorate, I was told by members of the congregation they did not believe in anointing with oil.
My question to them was “What do you do with James 5:14?”
They simply repeated their earlier statement on not believing in it.
And that is the problem today – lack of belief!
This Psalm compares fellowship of believers to the anointing of Aaron with oil.
This oil was fragrant with spices of myrrh, cinnamon, calamus, and cassia then poured over the head of Aaron, where it ran down his beard, onto his garment and soaking it to the very edge of his feet.
When poured out, oil penetrates and soaks in.
This is what God desires for His people – for His Spirit (the anointing) to pour over His people and penetrate and soak into us so we can dwell together in unity of the fellowship.