Exodus 29:1, 7 NKJV
[1] "And this is what you shall do to them to hallow them for ministering to Me as priests: Take one young bull and two rams without blemish, [7] And you shall take the anointing oil, pour it on his head, and anoint him.
Aaron was the high priest. He is the one who would be going into the holiest place. The anointing oil was to be poured on his head to set him apart for his ministry.
Spiritual parallel: Why the head? The head is a major starting point for the activity in the body. Four of our five senses are in the head - seeing, smelling, tasting and hearing. The brain is also in the head. It determines most of our activity and sends messages to other body parts to get things done. We can lose many body parts and still function. Our heads will help us figure out how to get by without the missing parts. However, if we lose our heads, none of the rest of our body parts will survive. The head is a critical body part. This can present a challenge for our spiritual lives. The head has to run things most of the time in the natural world. When we are dealing with spiritual things, the head has trouble backing down. We have to let the anointing hit our heads to put it in its place when we are dealing with spiritual things.
While the head plays a major role in the success of natural life, it can be a major hindrance when it comes to spiritual life. Our spirits are not guided by our physical senses, and the leading of the Holy Spirit often goes against reasoning. In order to minister accurately on behalf of the Lord, our heads need to be subject to our spirits. So it is fitting that the sanctification begin with the head. When we enter the holiest place, we must do so with great humility. We must not dare to come with an attitude of reasoning with God. We come to worship and obey. We come to surrender and serve. We come to wait on him – whatever He wants we are ready to give by the grace He gives us. The anointing enables us to do that. The anointing represents the Holy Spirit Who empowers us to do what is difficult or impossible for us to do on our own.