The Adornment of the Spiritual Marriage, by St. John of Rusybroeck (1293-1381)
Now if the spirit would see God with God in this Divine light without means, there needs must be on the part of man three things.
The first is that he must be perfectly ordered from without in all the virtues, and within must be unencumbered, and as empty of every outward work as if he did not work at all: for if his emptiness is troubled within by some work of virtue, he has an image; and as long as this endures within him, he cannot contemplate.
Secondly, he must inwardly cleave to God, with adhering intention and love, even as a burning and glowing fire which can never more be quenched. As long as he feels himself to be in this state, he is able to contemplate.
Thirdly, he must have lost himself in a Waylessness and in a Darkness, in which all contemplative men wander in fruition and wherein they never again can find themselves in a creaturely way. In the abyss of this darkness, in which the loving spirit has died to itself, there begin the manifestation of God and eternal life. For in this darkness there shines and is born an incomprehensible Light, which is the Son of God, in Whom we behold eternal life. And in this Light one becomes seeing; and this Divine Light is given to the simple sight of the spirit, where the spirit receives the brightness which is God Himself, above all gifts and every creaturely activity, in the idle emptiness in which the spirit has lost itself through fruitive love, and where it receives without means the brightness of God, and is changed without interruption into that brightness which it receives. Behold, this mysterious brightness, in which one sees everything that one can desire according to the emptiness of the spirit: this brightness is so great that the loving contemplative, in his ground wherein he rests, sees and feels nothing but an incomprehensible Light; and through that Simple Nudity which enfolds all things, he finds himself, and feels himself, to be that same Light by which he sees, and nothing else. And this is the first condition by which one becomes seeing in the Divine Light. Blessed are the eyes which are thus seeing, for they possess eternal life.
- Third Book, Chapter 1: Showing the three ways by which one enters the God-seeing life.