From a sermon by N. T. Wright, preached at Cathedral Church of Durham on Christmas Morning 2007:
Because what we are promised, in that strange phrase at the heart of John’s prologue, is a new kind of power: to all who received him, who believed in his name, he gave power to become children of God. Power to become children! There’s a paradox for you: power to become powerless, authority to be under authority. Ah, people will say, but children of God; yes, but the meaning of the word ‘God’ is now being redefined, in this very paragraph, so that we only really discover who God is when we look at Jesus, Jesus the helpless baby, Jesus the one who reveals God’s glory when he dies on the cross, Jesus the only begotten Son who has revealed the invisible God. And when we hear that gospel word, and discover that something new is happening within us, something is stirring which feels very like faith, and hope, and love, we know that a new kind of life has taken hold on us, meaning that we have indeed been born again, whether a moment before or a lifetime before, have been made new with a life which death cannot touch, a life which will lighten our path through whatever darkness lies ahead, a life which doesn’t spring from mere human possibilities – born, says John, not of blood or of the will of the flesh or of the will of man, but of God. Power to become children: that’s the promise of new birth, full of grace and truth.
“Part of the art of listening to scripture is learning to hear the multiple overtones in a single, simple phrase. And the Word became flesh and lived among us, says John: and we learn, and learn again, every Christmas, to hear in that great and simple statement all the glory of the new world, with its new possibilities: new life in Mary’s womb, new life within the increasingly dangerous public world which does its best to squash the rumour, and new life, please God, in our own hearts and lives and families and work. And the Word became flesh and lived among us. That is what we celebrate today: the new reality which leaves us no longer at ease in the old dispensation, but determined to live and rejoice and be part of his transforming work of new creation, so that though the world declares that it can’t see God and doesn’t know who he is we may declare, in what we are as well as what we say, that God the only Son, the Word made flesh, close to the Father’s heart, has made him known and will make him known. May that be true in us and through us this Christmas time and always.
The rest of the sermon can be found here: Power to Become Children.
From hence it manifestly appears, what is the nature of the new birth. It is that great change which God works in the soul when he brings it into life; when he raises it from the death of sin to the life of righteousness. It is the change wrought in the whole soul by the almighty Spirit of God when it is ‘created anew in Christ Jesus;’ when it is ‘renewed after the image of God, in righteousness and true holiness;’ when the love of the world is changed into the love of God; pride into humility; passion into meekness; hatred, envy, malice, into a sincere, tender, disinterested love for all mankind. In a word, it is that change whereby the earthly, sensual, devilish mind is turned into the ‘mind which was in Christ Jesus.’ This is the nature of the new birth: ‘So is every one that is born of the Spirit.’
— John Wesley, Sermon #45: “The New Birth.”