In "A Shepherd Looks at Psalm 23" author Phillip Keller says, the Shepherd must protect the sheep from nasal flies, because nasal flies will deposit larvae near the sheep's nostrils. Once hatched the adult flies crawl inside the sheep's nasal passages causing the sheep to hold their heads close to the ground. Sheep will run, stamp their feet, bang their heads on trees, hide in bushes and refuse to eat. They may feel as if they are going insane.
This is how many Christians feel when Satan, Lord of the flies may harass and torment them. It's been said that sheep may even kill themselves to relieve the harassing affect brought on by flies. Depression, anxiety, and suicidal thoughts are outward manifestations of spiritual (unseen) nasal flies as they hatch in a believer's life.
To protect sheep from flies the Good Shepherd applies a repellent to their heads. This is symbolic of God anointing the sheep of His pasture with the Holy Spirit. The Holy Spirit aides us against the flies/lies of the enemy who seek to cause us to bang our heads against the wall or cause us to bow our heads in oppression or depression, or tempt us to take our own lives because of life's circumstances.
When we speak to the Good Shepherd about our problems, the Holy Spirit will repel the flies. No weapon formed against us will prosper, says the Lord (Isaiah 54:17). Though the weapon is formed against us, the intended result will not come to pass. Because greater is He that is in us than He that's in the world (1 John 1:4)!
If you want to be delivered from invading pests sent to infest your thought life, you must come to the Shepherd. If you want to overcome negative circumstances that appear to be out of control, you must come to the Shepherd. He's waiting for you in lush green pastures to anoint your head with the oil of joy. Come to Him today!
