Christian spirituality is centered in God; in fact, its very goal is communion with God, which is attainable through the accomplishment of His will. To be what God wants us to be and to do what God want us to do is the sole meaning of our human existence. The fulfillment of the prayer “Thy will be done” is the heart and soul of all spiritual effort and activity.
In the Old Testament law, it is written:
I am the Lord your God; consecrate yourselves therefore, and be holy, for I am holy (Lev 11:44).
In the New Testament, the first letter of Saint Peter refers to this fundamental command of’ God.
... as He who called you is holy, be holy yourself in all your conduct; since it is written, “You shall be holy, for I am holy” (1 Pet 1:16).
That human beings should be holy by sharing in happiness of God Himself is the meaning of union with God. All are “called to be saints” (Rom 1:7) by becoming “partakers of the nature of God” (2 Pet 1:1). This is what Jesus meant when He said in Sermon on the Mount, “You, therefore, must be perfect, as your heavenly Father is perfect” (Mt 5:48).
The teaching that man must be holy and perfect like God Himself through the accomplishment of the will of God is the central teaching of the Orthodox Christian faith. This teaching has been stated in many different ways in the Orthodox spiritual tradition. Saint Maximus the Confessor (7th Century) said it this way: “Man is called to become by divine grace all that God Himself is by nature.” This means very simply that God wills and helps His creatures to be like He is, and that is the purpose of their being and life. As God is holy, man must be holy. As God is perfect, man must be perfect, pure, merciful, patient, kind, gentle, free, self-determining, ever-existing, and always, for eternity, the absolute superabundant realization of everything good in inexhaustible fulness and richness… so man must be this way as well, ever growing and developing in divine perfection and virtue for all eternity by the will and power of God Himself. The perfection of man is his growth in the unending perfection of God.