Now let us see, as far as the Lord deigns to help us to see, what the saints will be doing in their immortal and spiritual bodies, when the flesh will no longer be living “according to the flesh” but “according to the Spirit.” And yet, to tell the truth, I do not know what will be the nature of that activity, or rather of that rest and leisure. I have never seen it with my physical sight; and if I were to say that I had seen it with my mind–with my intellect–what is the human understanding, in capacity or in quality, to comprehend such unique perfection? For there will be that “peace of God which,” as the Apostle says, “is beyond all understanding.”
We must remember what a great apostle it was who said, “Our knowledge is partial, and our prophesying is partial, until perfection comes,” and, “We now see a dim reflection in a mirror; but then we shall see face to face.” This is how the holy angels see already, those who are called “our” angels, because we have been rescued from the power of darkness, we have received the pledge of the Spirit, and have been transferred to the kingdom of Christ, and so we already begin to belong to those angels with whom we shall share the possession of that holy and most delightful City of God. Thus those angels of God are also “our” angels, in the same way as the Christ of God is “our” Christ. They are God’s angels because they have not abandoned God; they are our angels because they have begun to have us as their fellow-citizens. And the Lord Jesus said: “Take care not to despise any of these little ones; for I tell you that their angels in heaven always see the face of my Father who is in heaven. ” Therefore we also shall see as they see already; but we do not as yet see like this. That is why the Apostle says, as I have already quoted, “Now we see a puzzling reflection in a mirror; but then we shall see face to face.” And so this vision is reserved for us as the reward of faith; and the apostle John speaks of the vision in these words: “When he is fully revealed, we shall be like him, because we shall see him as he is.”
—City of God 22.29