Oil is a widely understood symbol of the Holy Spirit and thus does not require a detailed explanation, but one scripture will suffice to link the Holy Spirit and oil directly:
The Spirit of the Lord is upon Me, because He has anointed Me to preach the gospel to the poor. He has sent Me to heal the brokenhearted, to preach deliverance to the captives and recovery of sight to the blind, to set at liberty those who are oppressed. . . . (Luke 4:18)
"The Spirit of the Lord" and the oil of anointing are directly linked. The oil of anointing stands as a physical representation of Jesus being given the Spirit to perform these functions for God in His service to man.
Acts 10:38 reveals another aspect of this symbolism: ". . . how God anointed Jesus of Nazareth with the Holy Spirit and with power, who went about doing good and healing all who were oppressed by the devil, for God was with Him." Again, reference is made to anointing—an act normally done with oil—with the Holy Spirit, and Peter adds "with power," a characteristic not included in Luke 4:18.
Though Jesus was bruised in service, He never lacked power. By contrast, we are rarely bruised, broken, or ground in service, but we are usually powerless. The truth is, the greatest zeal and knowledge are useless without God's Holy Spirit providing the right perspective, attitude, and intention for any service we perform.
John W. Ritenbaugh
The Offerings of Leviticus (Part Three): The Meal Offering