Bede's Ecclesiastical History of England, ed. by A.M. Sellar, , at sacred-texts.com
The same blessed Pope Gregory, at the same time, sent a letter to King Ethelbert, with many gifts of divers sorts; being desirous to glorify the king with temporal honours, at the same. time that he rejoiced that through his own labour and zeal he had attained to the knowledge of heavenly glory. The copy of the said letter is as follows:
"To the most glorious lord, and his most excellent son, Ethelbert, king of the English, Bishop Gregory. Almighty God advances good men to the government of nations, that He may by their means bestow the gifts of His lovingkindness on those over whom they are placed. This we know to have come to pass in the English nation, over whom your Highness was placed, to the end, that by means of the blessings which are granted to you, heavenly benefits might also be conferred on your subjects. Therefore, my illustrious son, do you carefully guard the grace which you have received from the Divine goodness, and be eager to spread the Christian faith among the people under your rule; in all uprightness increase your zeal for their conversion; suppress the worship of idols; overthrow the structures of the temples; establish the manners of your subjects by much cleanness of life, exhorting, terrifying, winning, correcting, and showing forth an example of good works, that you may obtain your reward in Heaven from Him, Whose Name and the knowledge of Whom you have spread abroad upon earth. For He, Whose honour you seek and maintain among the nations, will also render your Majesty’s name more glorious even to posterity.
"For even so the most pious emperor, Constantine, of old, recovering the Roman commonwealth from the false worship of idols, brought it with himself into subjection to Almighty God, our Lord Jesus Christ, and turned to Him with his whole mind, together with the nations under his rule. Whence it followed, that his praises transcended the fame of former princes; and he excelled his predecessors in renown as much as in good works. Now, therefore, let your Highness hasten to impart to the kings and peoples that are subject to you, the knowledge of one God, Father, Son, and Holy Ghost; that you may surpass the ancient kings of your nation in praise and merit, and while you cause the sins of others among your own subjects to be blotted out, become the more free from anxiety with regard to your own sins before the dread judgement of Almighty God.
"Willingly hear, devoutly perform, and studiously retain in your memory, whatsoever counsel shall be given you by our most reverend brother, Bishop Augustine, who is trained up in the monastic rule, full of the knowledge of Holy Scripture, and, by the help of God, endued with good works; for if you give ear to him when he speaks on behalf of Almighty God, the sooner will Almighty God hear his prayers for you. But if (which God forbid!) you slight his words, how shall Almighty God hear him on your behalf, when you neglect to hear him on behalf of God? Unite yourself, therefore, to him with all your mind, in the fervour of faith, and further his endeavours, by that virtue which God has given you, that He may make you partaker of His kingdom, Whose faith you cause to be received and maintained in your own.
"Besides, we would have your Highness know that, as we find in Holy Scripture from the words of the Almighty Lord, the end of this present world, and the kingdom of the saints, which will never come to an end, is at hand. But as the end of the world draws near, many things are about to come upon us which were not before, to wit, changes in the air, and terrors from heaven, and tempests out of the order of the seasons, wars, famines, pestilences, earthquakes in divers places; which things will not, nevertheless, all happen in our days, but will all follow after our days. If, therefore, you perceive that any of these things come to pass in your country, let not your mind be in any way disturbed; for these signs of the end of the world are sent before, for this reason, that we may take heed to our souls, and be watchful for the hour of death, and may be found prepared with good works to meet our Judge. Thus much, my illustrious son, I have said in few words, with intent-that when the Christian faith is spread abroad in your kingdom, our discourse to you may also be more copious, and we may desire to say the more, as joy for the full conversion of your nation is increased in our mind.
"I have sent you some small gifts, which will not appear small to you, when received by you with the blessing of the blessed Apostle, Peter. May Almighty God, therefore, perfect in you His grace which He has begun, and prolong your life here through a course of many years, and in the fulness of time receive you into the congregation of the heavenly country. May the grace of God preserve you in safety, my most excellent lord and son.
"Given the 22nd day of June, in the nineteenth year of the reign of our most religious lord, Mauritius Tiberius Augustus, in the eighteenth year after his consulship, and the fourth indiction."