With such like doctrines and saving words did Barlaam instruct the king's son, and fit him for holy Baptism, charging him to fast and pray, according to custom, several days: and he ceased not to resort unto him, teaching him every article of the Catholick Faith and expounding him the holy Gospel. Moreover he interpreted the Apostolick exhortations and the sayings of the Prophets: for, taught of God, Barlaam had alway ready on his lips the Old and New Scripture; and, being stirred by the Spirit, he enlightened his young disciple to see the true knowledge of God.
But on the day, whereon the prince should be baptized, he taught him, saying, "Behold thou art moved to receive the seal of Christ, and be signed with the light of the countenance of the Lord: and thou becomest a son of God, and temple of the Holy Ghost, the giver of life. Believe thou therefore in the Father, and in the Son, and in the Holy Ghost, the holy and life-giving Trinity, glorified in three persons and one Godhead, different indeed in persons and personal properties, but united in substance; acknowledging one God unbegotten, the Father; and one begotten Lord, the Son, light of light, very God of very God, begotten before all worlds; for of the good Father is begotten the good Son, and of the unbegotten light shone forth the everlasting light; and from very life came forth the life-giving spring, and from original might shone forth the might of the Son, who is the brightness of his glory and the Word in personality, who was in the beginning with God, and God without beginning and without end, by whom all things, visible and invisible, were made: knowing also one Holy Ghost, which proceedeth from the Father, perfect, life-giving and sanctifying God, with the same will, the same power, coeternal and impersonate. Thus therefore worship thou the Father, and the Son, and the Holy Ghost, in three persons or properties and one Godhead. For the Godhead is common of the three, and one is their nature, one their substance, one their glory, one their kingdom, one their might, one their authority; but it is common of the Son and of the Holy Ghost that they are of the Father; and it is proper of the Father that he is unbegotten, and of the Son that he is begotten, and of the Holy Ghost that he proceedeth.
"This therefore be thy belief; but seek not to understand the manner of the generation or procession, for it is incomprehensible. In uprightness of heart and without question accept the truth that the Father, and the Son, and the Holy Ghost, are in all points one except in the being unbegotten, and begotten, and proceeding; and that the only begotten Son, the Word of God, and God, for our salvation came down upon earth, by the good pleasure of the Father, and, by the operation of the Holy Ghost, was conceived without seed in the womb of Mary the holy Virgin and Mother of God, by the Holy Ghost, and was born of her without defilement and was made perfect man and that he is perfect God and perfect man, being of two natures, the Godhead and the manhood, and in two natures, endowed with reason, will, activity, and free will, and in all points perfect according to the proper rule and law in either case, that is in the Godhead and the manhood, and in one united person. And do thou receive these things without question, never seeking to know the manner, how the Son of God emptied himself, and was made man of the blood of the Virgin, without seed and without defilement; or what is this meeting in one person of two natures. For by faith we are taught to hold fast those things that have been divinely taught us out of Holy Scripture; but of the manner we are ignorant, and cannot declare it.
"Believe thou that the Son of God, who, of his tender mercy was made man, took upon him all the affections that are natural to man, and are blameless (he hungered and thirsted and slept and was weary and endured agony in his human nature, and for our transgressions was led to death, was crucified and was buried, and tasted of death, his Godhead continuing without suffering and without change; for we attach no sufferings whatsoever to that nature which is free from suffering, but we recognize him as suffering and buried in that nature which he assumed, and in his heavenly glory rising again from the dead, and in immortality ascending into heaven); and believe that he shall come again, with glory, to judge quick and dead, and by the words which himself knoweth, of that diviner body, and to reward every man by his own just standards. For the dead shall rise again, and they that are in their graves shall awake: and they that have kept the commandments of Christ, and have departed this life in the true faith shall inherit eternal life, and they, that have died in their sins, and have turned aside from the right faith, shall go away into eternal punishment. Believe not that there is any true being or kingdom of evil, nor suppose that it is without beginning, or self-originate, or born of God: out on such an absurdity! but believe rather that it is `the work of us and the devil, come upon us through our heedlessness, because we were endowed with free-will, and we make our choice, of deliberate purpose, whether it be good or evil. Beside this, acknowledge one Baptism, by water and the Spirit, for the remission of sins.
"Receive also the Communion of the spotless Mysteries of Christ, believing in truth that they are the Body and Blood of Christ our God, which he hath given unto the faithful for the remission of sins. For in the same night in which he was betrayed he ordained a new testament with his holy disciples and Apostles, and through them for all that should believe on him, saying, `Take, eat: this is my Body, which is broken for you, for the remission of sins.'