“After this manner, therefore, pray ye,” says He: “Our Father, which art in heaven.” See how He straightway stirred up the hearer, and reminded him of all God’s bounty in the beginning. For he who calls God Father, by him both remission of sins, and taking away of punishment, and righteousness, and sanctification, and redemption, and adoption, and inheritance, and brotherhood with the Only-Begotten, and the supply of the Spirit, are acknowledged in this single title. For one cannot call God Father, without having attained to all those blessings. Doubly, therefore, doth He awaken their spirit, both by the dignity of Him who is called on, and by the greatness of the benefits which they have enjoyed.
But when He says, “in Heaven,” He speaks not this as shutting up God there, but as withdrawing him who is praying from earth, and fixing him in the high places, and in the dwellings above.
He teaches, moreover, to make our prayer common, in behalf of our brethren also. For He says not, “my Father, which art in Heaven,” but, “our Father,” offering up his supplications for the body in common, and nowhere looking to his own, but everywhere to his neighbour’s good.
And by this He at once takes away hatred, and quells pride, and casts out envy, and brings in the mother of all good things, even charity, and exterminates the inequality of human things, and shows how far the equality reaches between the king and the poor man, if at least in those things which are greatest and most indispensable, we are all of us fellows.
For what harm comes of our kindred below, when in that which is on high we are all of us knit together, and no one hath aught more than another; neither the rich more than the poor, nor the master than the servant, neither the ruler than the subject, nor the king than the common soldier, nor the philosopher than the barbarian, nor the skillful than the unlearned?
For to all hath He given one nobility, having vouchsafed to be called the Father of all alike.
John Chrysostom (c.347-407): Homily 19 on St. Matthew's Gospel.