“Some Christians relate to God as slaves in the narrowest sense. They accept his will and obey his commandments and do what is required of them out of fear, out of the impending judgment, of the wrath to come (Matt. 3:7-12). But the spiritual life is not managed only through fear. Other Christians enter into the spiritual warfare as hirelings, as laborers or as soldiers in the pay of the king, as people who give themselves to God as for hire, accepting the responsibilities of the Christian life for the sake of reward (Lk. 6:35). Unlike the slave who acts out of fear, the hireling acts out of duty and obligation. He joins the ranks of God’s army to wage battle against the passions, against the evil forces of darkness that are in him and around him in the fallen world, because he is assured of God’s faithfulness to fulfill his promise to pay him just reward (1 Cor. 3:8; 2 John 8).
But greater perfection is expected of us. To be complete one must become, by grace, not only a slave or a hireling but also, and above all, a child of God, a brother – by adoption – and a friend of Christ. As a friend Christians accept God’s call with gladness of heart and act in all things out of love for the Master, who has loved them first (1 John 4:10). Friendship with God is unconditional because God’s love is unreserved, free, and absolute. Friends of Christ enjoy a deep, intimate personal relationship with him and come to know the hidden truths of the Gospel. They obey the commandments out of love, expecting nothing in return. “You are my friends if you do whatever I command you. No longer do I call you servants, for a servant does not know what his master is doing; but I have called you friends, for all things that I heard from my Father I have made known to you” (John 15:14-15).
(Alkiviadis C. Calivas, Aspects of Orthodox Worship, p. 32)