The Adornment of the Spiritual Marriage, by Jan van Ruysbroeck, , at sacred-texts.com
Now concerning the first point. Christ says: Behold. Whosoever wishes to see in a supernatural way in his inward exercises must have three things. The first is the light of Divine grace, and this in a more lofty degree than that which we can experience in the outward and active life without earnest inward diligence. The second thing is the casting out of all distracting images and attachments from the heart; so that the man may be free and imageless, released from all attachments, and empty of all creatures. The third thing is a free turning of the will, with a gathering together of all our powers, both bodily and ghostly, cleansed from every inordinate love. Thereby the will flows forth into the unity of God and into the unity of the mind; and thus the rational creature may obtain and possess the most high unity of God in a supernatural manner. For this God has created heaven and earth and everything; and for this reason He became man, and taught us, and lived for our sake, and has Himself become the Way to the unity. And He died in the bonds of love, and has ascended and has opened to us that very unity, in which we may possess eternal bliss.