Hagios means holy — set apart, distinct, belonging to God. It describes God's own character (Holy, holy, holy is the Lord), the Holy Spirit (Pneuma Hagion), and, remarkably, ordinary believers, who are called hagioi — saints. In the New Testament a saint is not a spiritual elite but simply one set apart for God by his grace.
The call to holiness flows from God's own nature: be ye holy, for I am holy. This is not a summons to grim perfectionism but to belonging — to living as those who are set apart for God and increasingly shaped into his likeness. Holiness is both a gift already given in Christ and a life we grow into by the Spirit.
Hagios in Scripture
Because it is written, Be ye holy; for I am holy.