The Adornment of the Spiritual Marriage, by Jan van Ruysbroeck, , at sacred-texts.com
From this temperance there springs purity both of soul and of body, for none can be perfectly pure in body and in soul save him who is temperate in body and in soul.
Purity of spirit is this: that a man should not cleave to any creature with desirous affection, but to God alone; for we should use all creatures, but enjoy only God. Purity of spirit makes a man cleave to God, above all understanding, and above all feelings, and above all the gifts which God may pour into his soul: for all that a creature receives in his understanding and in his feeling, purity will pass by, to rest in God. Go therefore to the Sacrament of the Altar, not for the sake of refreshment, nor because of desire, nor for pleasure, nor for peace, nor for satisfaction, nor for sweetness, nor for anything else than the glory of God and your own growth in all virtues. This is purity of spirit.
Purity of heart is this: that a man, in every bodily temptation or natural inclination, of his own free will, and with an ever-renewed confidence and without hesitation, turns to God; with an ever-renewed faithfulness and with a firm will ever to remain with Him. For consenting to those sins or satisfactions, which the bodily nature seeks like a beast, is a departure from God.
Purity of body is this: that a man withdraws from, and bewares of, all unchaste deeds, in whatsoever manner they be, which his conscience teaches and declares to be unchaste, and contrary to the commandments, the honour, and the will of God.
By these three kinds of purity the seventh mortal sin is overcome and cast out; that is, Unchastity. And this is a consenting and turning of the spirit from God to some creaturely thing; it is the unchaste work of the body contrary to the dispensation of Holy Church; it is a sensual dwelling of the heart upon the taste or enjoyment of some creature, whatsoever it be. But thereby I do not mean those sudden movements of appetite and desire, which no one can prevent.
Now you should know that purity of spirit keeps a man in the likeness of God, untroubled by any creature and inclined towards God, and united with Him.
Purity of body is likened to the whiteness of lilies and to the cleanness of the angels. In withstanding, it is likened to the redness of roses and to the nobleness of martyrs. If it is kept for the love and the glory of God, it is perfect. And so it is likened to the sunflower, for it is one of the highest ornaments of nature.
Purity of heart works a renewal and increase of the grace of God. By purity of heart all the virtues are prompted, practised and preserved. It guards and keeps the senses from without; it quells and restrains the animal lusts from within; it is an adornment of all inwardness. And it is the door of the heart; barred against all earthly things and all deceit, but opened to all heavenly things and to all truth. And of all such Christ says: Blessed are the pure in heart: for they shall see God; and in this vision consist our eternal joy, our reward and our entrance into bliss. Therefore men should be sober and temperate in all things, and beware of all intercourse and occasion whereby purity, whether of soul or of body, may be defiled.