The English historian Bede records copies of letters sent by Boniface (the Bishop of Rome) in 625 AD to King Edwin and Queen Ethelberga explaining the Gospel and why it ought to be believed. While it perhaps is not as clearly defined a Gospel as we post-Reformation folks would like, all the key aspects are still there, including:
-Christ is the only way to life and salvation;
-God is the Creator;
-God is Trinity;
-Christianity is opposed to the worship of idols and images;
-Salvation is through Christ's death on the cross;
-Salvation is by grace alone;
To the illustrious Edwin, king of the English, Bishop Boniface, the servant of the servants of God. Although the power of the Supreme Deity cannot be expressed by human speech, as consisting in its own greatness, and in invisible and unsearchable eternity, so that no sharpness of wit can comprehend or express it; yet in regard that the goodness of God, to give some notion of itself, having opened the doors of the heart, has mercifully, by secret inspiration, infused into the minds of men such things as He is willing shall be declared concerning Himself, we have thought fit to extend our priestly care to make known to you the fulness of the Christian faith; to the end that, informing you of the Gospel of Christ, which our Saviour commanded should be preached to all nations, they might offer to you the cup of life and salvation.
"Thus the goodness of the Supreme Majesty, which, by the word of his command, made and created all things, the heaven, the earth, the sea, and all that is in them, disposing the order by which they should subsist, hath, with the counsel of his co-eternal Word, and the unity of the Holy Spirit, formed man after his own likeness, out of the slime of the earth; and granted him such super-eminent prerogative, as to place him above all others; so that, observing the command which was given him, his continuance should be to eternity. This God,-Father, Son, and Holy Ghost, which is an undivided Trinity,- mankind, from the east unto the west, by confession of faith to the saving of their souls, do worship and adore as the Creator of all things, and their own Maker; to whom also the heights of empire, and the powers of the world, are subject, because the bestowal of all kingdoms is granted by his disposition. It hath pleased Him, therefore, of his great mercy, and for the greater benefit of all his creatures, by his Holy Spirit wonderfully to kindle the cold hearts also of the nations seated at the extremities of the earth in the knowledge of Himself.
"For we suppose your excellency has, from the country lying so near, fully understood what the clemency of our Redeemer has effected in the enlightening of our glorious son, King Eadbald, and the nations under his subjection; we therefore trust, with assured confidence of celestial hope, that his wonderful gift will be also conferred on you; since we understand that your illustrious consort, which is known to be a part of your body, is illuminated with the reward of eternity, through the regeneration of holy baptism. We have, therefore, taken care by these presents, with all possible affection, to exhort your illustrious selves, that, abhorring idols and their worship, and contemning the follies of temples, and the deceitful flatteries of auguries, you believe in God the Father Almighty, and his Son Jesus Christ, and the Holy Ghost, to the end that, being discharged from the bonds of captivity to the Devil, by believing you may, through the co-operating power of the holy and undivided Trinity, be partaker of the eternal life.
"How great guilt they lie under, who adhere to the pernicious superstitions and worship of idolatry, appears by the examples of the perdition of those whom they worship. Wherefore it is said of them by the Psalmist, 'All the gods of the Gentiles are devils, but the Lord made the heavens.' And again, 'they have eyes and do not see, they have ears and do not hear, they have noses and do not smell, they have hands and do not feel, they have feet and do not walk. Therefore they are like those that confide in them.' For how can they have any power to yield assistance, that are made for you out of corruptible matter, by the hands of your inferiors and subjects, to wit, on whom you have by human art bestowed an inanimate similitude of members? Who, unless they be moved by you, will not be able to walk; but, like a stone fixed in one place, being so formed, and having no understanding, but absorbed in insensibility, have no power of doing harm or good. We cannot, therefore, upon mature deliberation, find out how you come to be so deceived as to follow and worship those gods, to whom you yourselves have given the likeness of a body.
"It behooves you, therefore, by taking upon you the sign of the holy cross, by which the human race is redeemed, to root out of your hearts all those arts and cunning of the Devil, who is ever jealous of the works of the Divine goodness, and to lay hold and break in pieces those which you have hitherto made your material gods. For the very destruction and abolition of these, which could never receive life or sense from their makers, may plainly demonstrate to you how worthless they were which you till then had worshipped, when you yourselves, who have received life from the Lord, are certainly better than they, as-Almighty God has appointed you to be descended after many ages and through many generations, from the first man whom He formed. Draw near, then, to the knowledge of Him who created you, who breathed the breath of life into you, who sent his only-begotten Son for your redemption, to cleanse you from original sin, that being delivered from the power of the Devil's wickedness, He might bestow on you a heavenly reward.
Hear the words of the preachers, and the Gospel of God, which they declare to you, to the end that, believing, as has been said, in God the Father Almighty, and in Jesus Christ his Son, and the Holy Ghost, and the indivisible Trinity, having put to flight the sensualities of devils, and driven from you the suggestions of the venomous and deceitful enemy, and being born again by water and the Holy Ghost, you may, through his assistance and bounty, dwell in the brightness of eternal glory with Him in whom you shall believe. We have, moreover, sent you the blessing of your protector, the blessed Peter, prince of the apostles, that is, a shirt, with one gold ornament, and one garment of Ancyra, which we pray your highness to accept with the same goodwill as it is friendly intended by us."
THE COPY OF THE LETTER OF THE MOST BLESSED AND APOSTOLIC BONIFACE, POPE OF THE CITY OF ROME, TO ETHELBERGA, KING EDWIN'S QUEEN.
"To the illustrious lady his daughter, Queen Ethelberga, Boniface, bishop, servant of the servants of God: The goodness of our Redeemer has with much providence offered the means of salvation to the human race; which He rescued, by the shedding of his precious blood, from the bonds of captivity to the Devil; so that making his name known in divers ways to the Gentiles, they might acknowledge their Creator by embracing the mystery of the Christian faith, which thing, the mystical purification of your regeneration plainly shows to have been bestowed upon the mind of your highness by God's bounty. Our mind, therefore, has been much rejoiced in the benefit of our Lord's goodness, for that He has vouchsafed, in your conversion, to kindle a spark of the orthodox religion, by which He might the more easily inflame in his love the understanding, not only of your glorious consort, but also of all the nation that is subject to you.
"For we have been informed by those, who came to acquaint us with the laudable conversion of our illustrious son, King Eadbald, that your highness, also, having received the wonderful sacrament of the Christian faith, continually excels in the performance of works pious and acceptable to God. That you likewise carefully refrain from the worship of idols, and the deceits of temples and auguries, and having changed your devotion, are so wholly taken up with the love of your Redeemer, as never to cease lending your assistance for the propagation of the Christian faith. And our fatherly charity having earnestly inquired concerning your illustrious husband, we were given to understand that he still served abominable idols, and would not yield obedience or give ear to the voice of the preachers. This occasioned us no small grief, for that part of your body still remained a stranger to the knowledge of the supreme and undivided Trinity. Whereupon we, in our fatherly care, did not delay to admonish your Christian highness, exhorting you, that, with the help of the Divine inspiration, you will not defer to do that which, both in season and out of season, is required of us; that with the co-operating power of our Lord and Saviour Jesus Christ, your husband also may be added to the number of Christians; to the end that you may thereby enjoy the rights of marriage in the bond of a holy and unblemished union. For it is written, 'They two shall be in one flesh How can it be said, that there is unity between you, if he continues a stranger to the brightness of your faith, by the interposition of dark and detestable error?
"Wherefore, applying yourself continually to prayer, do not cease to beg of the Divine Mercy the benefit of his illumination; to the end, that those whom the union of carnal affection has made in a manner but one body, may, after death, continue in perpetual union, by the bond of faith. Persist, therefore, illustrious daughter, and to the utmost of your power endeavour to soften the hardness of his heart by insinuating the Divine precepts; making him sensible how noble the mystery is which you have received by believing, and how wonderful is the reward which, by the new birth, you have merited to obtain. Inflame the coldness of his heart by the knowledge of the Holy Ghost, that by the abolition of the cold and pernicious worship of paganism, the heat of Divine faith may enlighten his understanding through your frequent exhortations; that the testimony of the holy Scripture may appear the more conspicuous, fulfilled by you, 'The unbelieving husband shall be saved by the believing wife.' For to this effect you have obtained the mercy of our Lord's goodness. that you may return with increase the fruit of faith, and the benefits entrusted in your hands; for through the assistance of his mercy we do not cease with frequent prayers to beg that you may be able to perform the same.
Having premised thus much, in pursuance of the duty of our fatherly affection, we exhort you, that when the opportunity of a bearer shall offer, you will as soon as possible acquaint us with the success which the Divine Power shall grant by your means in the conversion of your consort, and of the nation subject to you; to the end, that our solicitude, which earnestly expects what appertains to the salvation of you and yours, may, by hearing from you, be set at rest; and that we, discerning more fully the brightness of the Divine propitiation diffused in you, may with a joyful confession abundantly return due thank to God, the Giver of all good things, and to St. Peter the prince of apostles. We have, moreover, sent you the blessing of your protector, St. Peter, the prince of the apostles, that is, a silver looking-glass, and a gilt ivory comb, which we entreat your glory will receive with the same kind affection as it is known to be sent by us."