From St Cyprian’s treatise on the Lord’s Prayer:
How great is the Lord’s indulgence! How kindly he bends down to us, how he overflows with goodness towards us! For he wishes us to pray in the sight of God in such a way as to call God Father and to call ourselves sons of God, just as Christ is the Son of God. No-one would have dared to claim such a name in prayer, unless he himself had given us permission to pray this. And so, beloved brethren, we should know and remember that when we call God our Father, we must behave as children of God, so that whatever pleasure we take in having God for our Father, he may take the same pleasure in us.
Let us behave like temples of God, so that it may be clear that God dwells in us. Let our doings not fall away from the Spirit, but let us, who have begun to be heavenly and spiritual, consider and do nothing but heavenly and spiritual things. As the Lord God himself has said: Those who honour me, I will honour them; but those who despise me will be despised. And the blessed apostle has also said in his letters: You are not your own property: you have been bought at a great price. Glorify God and carry him in your bodies.
After this we say Hallowed be thy name. This is not because we want God to be made holy by our prayers: what we are asking God is that his name should be hallowed within us. After all, how can anything be needed to sanctify God, who himself is the source of sanctity? But because he says be holy, as I am holy, we ask and beg of him that we, who have been sanctified in baptism, may continue in that which we have begun to be. And this we pray daily, for our need is for daily sanctification so that we who daily fall away may wash away our crimes by continual sanctification.
As for the nature of the sanctification that comes to us from God, the Apostle tells us when he says: They will not inherit the kingdom of God, who fornicate, or worship idols, or commit adultery; catamites or sodomites, thieves, cheats, drunkards, slanderers or extortioners. You were like this once, but you were washed, you were justified, you were made holy in the name of the Lord Jesus Christ and in the Spirit of our God. He says that we are sanctified in the name of our Lord Jesus Christ and by the Spirit of our God. We pray that this sanctification may remain with us; and because our Lord and Judge warns the man who was healed and given life by him not to sin again, lest something worse happen to him, we make this prayer without ceasing, we beg for it day and night, that the sanctification and life that comes from God may be preserved by his protection.