"Then the eyes of the blind shall be opened, and the ears of the deaf shall be unstopped. Then shall the lame man leap as an hart, and the tongue of the dumb sing: for in the wilderness shall waters break out, and streams in the desert." - Isaiah 35:5,6
To be holy is to display His nature. He is undefiled and without impurity and He desires us to be the same.
In the Complete Word Study Dictionary, holiness in Isaiah 35:8 means, "a holy thing and sacredness. It indicates something consecrated and set aside for sacred use only; it was not to be put into common use, for if it was, it became profaned and common, not holy." This is a wake-up call. As born again believers we are called to be set aside for sacred use. We are not made for common use. We are not to look and act like the world. We belong to another Kingdom. We are not our own.
As citizens of Heaven, we are to demonstrate intimacy with God and the fragrance of having been with Jesus. You can be in the wilderness and yet experience the bloom of that fellowship with Him. We demonstrate the Kingdom of God in obeying the commission of Jesus Christ which includes discipling baby Christians into their inheritance in Christ, laying hands on the sick, and walking in the Spirit in addition to preaching the Gospel.
Without being set apart for uncommon use, we will yield to passions and things that will pollute our union with God.