Ephesians 1:4

Ephesians 1:4 Even as He chose us in Him before the foundation of the world to be holy and without blemish before Him in love,

Holy not only means sanctified, separated unto God, but also different, distinct, from everything that is common. Only God is different, distinct, from all things. Hence, He is holy; holiness is His nature.

The way God makes us holy is to impart Himself, the Holy One, into us so that our whole being may be permeated and saturated with His holy nature. For us, God's chosen ones, to be holy is to partake of His divine nature and to have our whole being permeated with God Himself. 

- "Life Study of Ephesians" P24