St Cyprian (c. 200 - 258) on the Our Father:

He was "the second African theologian" after Tertullian, whom he venerated as "the Master". He had none of Tertullian's fire, but he had a kind and gentle spirit. He was no sooner elected bishop of Carthage than the Decian persecution broke out. Cyprian found a safe place from which to instruct the faithful - an expedient that was not appreciated by all. Later, however, when plague broke out he gave heroic example of caring for the sick. He was martyred in 258.

      Before all things, the Teacher of Peace and the Master of Unity would not have prayer to be made single and individually, as for one who prays for him or herself alone. For we do not say 'My Father, who art in heaven,' nor 'Give me this day my daily bread'; nor does each one ask that only his or her own debt should be forgiven…. Our prayer is public and common; and when we pray we pray not for one but for the whole people, because we the whole people are one. The God of peace and the teacher of concord, who taught unity, willed that one should thus pray for all, even as he himself bore us all in one….
     'Hallowed be thy name': not that we wish God to be sanctified by our prayers, but that we ask to keep his name holy in us. Besides, who could sanctify God who is the source of holiness? But he has said, "Be holy as I am holy," and so we pray for perseverance in the holiness which we received at baptism. We ask for this every day because we who offend every day need a daily sanctification, a continual hallowing purification….
     'Thy Kingdom come': we beg that God's Kingdom be revealed to us. For when did God not reign? When did he not possess his Kingdom which always was and ever shall be? God has promised a Kingdom to us, Christ has gained it by his passion and blood. We pray for its coming…in us.
     'Thy will be done on earth as it is in heaven': God may do what he wishes, who can hinder him in that? But we pray that we may be able to fulfil his will in us…. What is the will of God? It is what Christ did and taught: humility in conduct, steadiness in faith, modesty in words, justice in deeds, mercy in works, discipline in habits. It is to be innocent of wrongdoing and to be patient when wrong is done to us and to remain at peace with our brethren. It is to love God with all our heart….
     'Give us this day our daily bread': This may be understood both spiritually and literally…. 1. Christ is the bread of life…. We are in Christ and receive the Eucharist daily as the food of salvation…. 2. "The one who does not renounce the world cannot be my disciple," Jesus said. We who have renounced the world and its riches and pomps should seek only our food and keep. The new followers of Christ, forsaking all in obedience to him, should be moderate in their requirements: they ought to ask only for their daily bread. "Do not worry about tomorrow, for tomorrow will take care of itself." Disciple should not worry about tomorrow, but they are entitled to pray for today.
     'Forgive us our trespasses…': We have asked for food. Now we ask for forgiveness, so that we who are fed by God may live in him….Remember, our entreaties for forgiveness will not be heard unless we deal forgivingly with those who sin against us. God does not accept the sacrifice of the man who is at variance with his brother. He orders him to leave the altar and first to be reconciled.
     'Lead us not into temptation': The enemy can do nothing against us without God's permission…. Praying that we may not come into temptation reminds us of our inconstancy and weakness.
     'Deliver us from evil': Having said that, there is nothing left to ask for. With God's protection we stand safe and secure against all the devices of the devil and the world. Who can fear this life, if God is his life-guardian?"

In their many different idioms the classical spiritual writers have attempted to throw light on the eternal question of union with God. 
Every month we give you a brief passage from a spiritual classic.